Nuclear weapons and the United Kingdom

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United Kingdom
Location of United Kingdom
Nuclear program start date10 April 1940
First nuclear weapon test3 October 1952
First fusion weapon test15 May 1957
Last nuclear test26 November 1991
Largest yield testMt (13 PJ) (28 April 1958)
Total tests45 detonations
Peak stockpile520 warheads (1970s)
Current stockpile (usable and not)215 warheads (2016)[1][2]
Current strategic arsenal120 usable warheads (2016)[1][2]
Maximum missile range12,000 km (7,500 mi) (UGM-133 Trident II)[3]
NPT partyYes (1968, one of five recognised powers)

In October 1952, the United Kingdom (U.K.) became the third country to independently develop and test nuclear weapons. It is one of the five nuclear-weapon states under the Treaty on the Non-Proliferation of Nuclear Weapons and a permanent member of the United Nations Security Council. Since the 1958 US–UK Mutual Defence Agreement, the United States and the UK have cooperated extensively on nuclear security matters. The special relationship between the two countries has involved the exchange of classified scientific data and materials such as plutonium.

The UK had a stockpile of 215 thermonuclear warheads, of which 120 were operational, as of 2016, but the country has refused to declare the exact size of its arsenal.[1][2][4] Since 1998, the Trident nuclear programme has been the only operational nuclear weapons system in British service. The delivery system consists of four Vanguard class submarines based at HMNB Clyde in Scotland. Each submarine is armed with up to sixteen Trident II missiles, each carrying warheads in up to eight Multiple independently targetable reentry vehicles. With at least one submarine always on patrol, the Vanguards perform a strategic deterrence role and are also believed to have a sub-strategic capability. Unlike the other permanent members of the Security Council, the U.K. operates only a submarine-based delivery system, having decommissioned its tactical WE.177 free-fall bombs in 1998.

The UK has not had a program to develop an independent delivery system since the cancellation of the Blue Streak (missile) in 1960. Instead, it has purchased US delivery systems for UK use, fitting them with warheads designed and manufactured by the U.K.'s Atomic Weapons Establishment (AWE) and its predecessor. In 1974, a US proliferation report discussing British nuclear and missile development noted that "In many cases, it is based on technology received from the US and could not legitimately be passed on without US permission."[5]

As of 2006, the AWE was undertaking research dedicated largely to providing new warheads.[6] On 4 December 2006, Prime Minister Tony Blair announced plans for a new class of nuclear missile submarines.[7]

Number of warheads


Faslane Naval Base, HMNB Clyde, Scotland. Home of the Vanguard-class submarines which carry the UK's current nuclear arsenal.

Since 1969 the United Kingdom has always had at least one ballistic-missile submarine on patrol, giving it a nuclear deterrent that is, what the Defence Council described in 1980 as, "effectively invulnerable to pre-emptive attack".[8] In the Strategic Defence Review published in July 1998, the government stated that once the Vanguard submarines became fully operational (the fourth and final one, Vengeance, entered service on 27 November 1999), it would "maintain a stockpile of fewer than 200 operationally available warheads".[9] The Stockholm International Peace Research Institute has estimated the figure as about 170, consisting of 144 deployed weapons plus an extra 15 percent as spares.[10]

At the same time, the UK government indicated that warheads "required to provide a necessary processing margin and for technical surveillance purposes" were not included in the "fewer than 200" figure.[11] As recently declassified archived documents on Chevaline make clear, the 15% excess (referred to by SIPRI as for spares) is normally intended to provide the 'necessary processing margin', and 'surveillance rounds do not contain any nuclear material, being completely inert. These surveillance rounds are used to monitor deterioration in the many non-nuclear components of the warhead, and are best compared with inert training rounds.' The SIPRI figures correspond accurately with the official announcements and are likely to be the most accurate. The Natural Resources Defense Council speculates that a figure of 200 is accurate to within a few tens.[12]

In 2008, the National Audit Office stated that the UK stockpile was of fewer than 160 operationally available nuclear warheads.[13] During a debate on the Queen's Speech on 26 May 2010, Foreign Secretary William Hague reiterated that the UK has no more than 160 operationally available warheads, and announced that the total number will not exceed 225.[14]


Until the 1990s the UK deployed a wide variety of nuclear weapons around the world, such as V bombers in Singapore in the 1960s, aircraft on Cyprus and on Royal Navy carriers in the 1960s and 1970s.[15] Until August 1998, the UK retained the WE.177 nuclear weapon manufactured in the mid-1960s to late 1970s, in air-dropped free-fall bomb and depth charge versions.[16] Its withdrawal left the four Vanguard class submarines, which replaced the Polaris ones in the early 1990s, as Britain's only nuclear weapons platform. It has been estimated by the Bulletin of the Atomic Scientists that the United Kingdom has built around 1,200 warheads since the first Hurricane device of 1952.[17] In terms of number of warheads, the UK arsenal was at its maximum size of about 520 in the 1970s, but this figure does not include the large numbers of US-owned warheads, bombs, nuclear depth bombs supplied from US stocks in Europe for use by NATO allies. At its peak, these numbered 327 for the British Army of the Rhine in Germany alone.

Weapons tests

The United Kingdom tested its first nuclear weapons in Australia during the 1950s, on the Montebello Islands (Western Australia) and at the Woomera Prohibited Area (South Australia).

The first detonation, codenamed Operation Hurricane, occurred on 3 October 1952, in a shallow bay on Trimouille Island. Two further tests were held on the Montebello Islands during 1956. The second of these, codenamed "G2", included the largest nuclear explosion in Australia, with a yield of 98 kilotons.

Seven further nuclear tests were conducted on the Australian mainland between 1955 and 1963, within the Woomera Prohibited Area, at Emu Field and Maralinga in South Australia.

The first British hydrogen bombs were tested during Operation Grapple at Malden Island and Christmas Island in the Central Pacific Ocean. The operation consisted of nine tests in the period 1957–1959, ultimately proving that the UK had developed thermonuclear weapons.

Different sources give the total number of test explosions that the UK has conducted as either 44[18][19] or 45.[20][21] The 24 tests from December 1962 onwards were in conjunction with the United States at the Nevada Test Site[22][23] with the final test being the Julin Bristol shot which took place on 26 November 1991.[24]

Because Britain did not test as often as the United States for financial and political reasons, and did not have the Americans' state-of-the-art computer facilities, British weapons design depended more on theoretical understanding, with potential for both greater advances and greater risks between tests.[25]The low number of UK tests is misleading when compared to the large number of tests carried out by the US, the Soviet Union, China, and especially France, because the UK has had extensive access to US test data, obviating the need for UK tests. An added factor is that many tests were for 'weapon effects tests': tests not of the nuclear device itself, but of the nuclear effects on hardened components designed to resist ABM attack. Numerous such 'effects' tests were done in support of the Chevaline programme especially, and there is some evidence that some were permitted for the French programme to harden their RVs and warheads; because most French tests were under the ocean floor, access to measure 'weapon effects' was nearly impossible.[26] An independent test programme would have seen the UK numbers soar to French levels.

The UK government signed the Partial Test Ban Treaty on 5 August 1963[27] along with the United States and the Soviet Union which effectively restricted it to underground nuclear tests by outlawing testing in the atmosphere, underwater, or in outer space. The UK signed the Comprehensive Test Ban Treaty on 24 September 1996[28] and ratified it on 6 April 1998,[29] having passed the necessary legislation on 18 March 1998 as the Nuclear Explosions (Prohibition and Inspections) Act 1998.

A series summary of British testing is shown here: United Kingdom's nuclear testing series. Note that the Vixen safety tests are not usually listed along with the "real" nuclear testing in lists of British tests. However, they are included in totals for US, USSR, Chinese and French testing.[30] Their outcomes are not known, though they are for most other safety tests.

Nuclear defence

Warning systems

This solid-state phased array radar at RAF Fylingdales in North Yorkshire is a UK-controlled early warning station and part of the American-controlled Ballistic Missile Early Warning System.

The UK has relied on the Ballistic Missile Early Warning System (BMEWS) and, in later years, Defense Support Program (DSP) satellites for warning of a nuclear attack. Both of these systems are owned and controlled by the United States, although the UK has joint control over UK-based systems. One of the four component radars for the BMEWS is based at RAF Fylingdales in North Yorkshire.

In 2003 the UK government stated that it will consent to a request from the US to upgrade the radar at Fylingdales for use in the US National Missile Defense system.[31]

Nevertheless, missile defence is not currently a significant political issue within the UK. The ballistic missile threat is perceived to be less severe, and consequently less of a priority, than other threats to its security.[32]

Attack scenarios

During the Cold War, a significant effort by government and academia was made to assess the effects of a nuclear attack on the UK. There were four major exercises:

  • Exercise Inside Right took place on 6–26 October 1975.
  • Exercise Scrum Half was conducted in 1978.
  • Exercise Square Leg was conducted in 1980. The scenario involved around 130 warheads with a total yield of 205 megatons (69 ground burst, 62 air burst) with an average of 1.5 megatons per bomb. The exercise was criticised as unrealistic as an actual exchange would be much larger, with one academic describing a 200-megaton attack as an "extremely low figure and one which we find very difficult to take seriously",[33] and did not include targets in Inner London such as Whitehall.[34] Even so, the effect of the limited attack in Square Leg was estimated to be 29 million dead (53 percent of the population) and 6.4 million seriously injured.[35]
  • Exercise Hard Rock was a combined communications and civil defence exercise planned for September and October 1982. It assumed a conventional war in Europe lasting two to three days, during which the UK would be attacked with conventional weapons, then a limited nuclear exchange, with 54 nuclear warheads used against military targets in the UK. 250,000 people protested against the exercise and 24 councils refused to participate.[35] The limited scenario still assumed casualties of 7.9 million dead and 5 million injured.[35] The scenario was ridiculed by the Campaign for Nuclear Disarmament and the exercise was postponed indefinitely.[36] The New Statesman later claimed the Ministry of Defence insisted on having a veto over proposed targets in the exercise and several were removed to make them politically more acceptable; for example, the nuclear submarine base HMNB Clyde was removed from the target list.[37]

In the early 1980s it was thought an attack causing almost complete loss of life could be achieved with the use of less than 15 percent of the total nuclear yield available to the Soviets.[33]

Civil defence

During the Cold War, various governments developed civil defence programmes aimed to prepare civilian and local government infrastructure for a nuclear strike on the UK. A series of seven Civil Defence Bulletin films were produced in 1964, and in the 1980s the most famous such programme was probably the series of booklets and public information films entitled Protect and Survive.

If the country was ever faced with an immediate threat of nuclear threat or complete annihilation, a copy of this booklet would be distributed to every household as part of a public information campaign which would include announcements on television and radio and in the press. The booklet has been designed for free and general distribution in that event. It is being placed on sale now for those who wish to know what they would be advised to do at such a time.[38]

The booklet contained information on building a nuclear refuge within a so-called "fall-out room" at home, sanitation, limiting fire hazards, and descriptions of the audio signals for attack warning, fall-out warning and all clear. It was anticipated that families might need to stay in their fall-out room for up to 14 days after an attack almost without leaving it at all.

The government also prepared a recorded announcement which was to have been broadcast by the BBC if a nuclear attack ever did occur.[39]

Sirens left over from the London Blitz during World War II[citation needed] were also to be used to warn the public. The system was mostly dismantled in 1993.

Historical weapons programmes

The United Kingdom worked in partnership with the United States and Canada on the Manhattan Project, resulting in the development of the first nuclear weapons, and the first-ever nuclear detonation at the Trinity test of 16 July 1945.

Tube Alloys

The neutron was discovered by James Chadwick at the Cavendish Laboratory at the University of Cambridge in February 1932,[40] and in April 1932, his Cavendish colleagues John Cockcroft and Ernest Walton split lithium atoms with accelerated protons.[41] In December 1938, Otto Hahn and Fritz Strassmann at Hahn's laboratory in Berlin-Dahlem bombarded uranium with slow neutrons,[42] and discovered that barium had been produced, and therefore that the uranium nucleus had been split.[43] Hahn wrote to his colleague Lise Meitner, who, with her nephew Otto Frisch, developed a theoretical justification for the process based on Niels Bohr's liquid drop model of the nucleus, which they published in Nature in 1939.[44] By analogy with the division of biological cells, they named the process "fission".[45]

The discovery of fission raised the possibility that an extremely powerful atomic bomb could be created.[46] The term was already familiar to the British public through the writings of H. G. Wells, with a continuously-exploding bomb in his 1913 novel The World Set Free.[47] George Paget Thomson, at Imperial College London, and Mark Oliphant, an Australian physicist at the University of Birmingham, were tasked with carrying out a series of experiments on uranium.[48] Oliphant delegated the task to two German refugee scientists, Rudolf Peierls and Frisch, who ironically could not work on the university's secret projects like radar because they were enemy aliens and therefore lacked the necessary security clearance.[49] They calculated the critical mass of a metallic sphere of pure uranium-235, and found that instead of tons, as everyone had assumed, as little as 1 to 10 kilograms (2.2 to 22.0 lb) would suffice, which would explode with the power of thousands of tons of dynamite.[50][51]

Oliphant took the Frisch–Peierls memorandum to Sir Henry Tizard, the chairman of the Tizard Committee,[52] and the MAUD Committee was established to investigate further.[53] It directed an intensive research effort, and in July 1941, produced two comprehensive reports that reached the conclusion that an atomic bomb was not only technically feasible, but could be produced before the war ended, perhaps in as little as two years. The Committee unanimously recommended pursuing the development of an atomic bomb as a matter of urgency, although it recognised that the resources required might be beyond those available to Britain.[54][55] A new directorate known as Tube Alloys was created to coordinate this effort. Sir John Anderson, the Lord President of the Council, became the minister responsible, and Wallace Akers from Imperial Chemical Industries (ICI) was appointed the director of Tube Alloys.[56]

Manhattan Project

Groves sits a completely clean desk. Chadwick, seated next to him, looks on. Tolman sits on the other side, and Smyth leans over the table.
James Chadwick (left), the head of the British Mission, with Major General Leslie R. Groves, Jr., the director of the Manhattan Project; Richard C. Tolman, his scientific advisor; and Henry DeWolf Smyth

In July 1940, Britain had offered to give the United States access to its scientific research,[57] and the Tizard Mission's John Cockcroft briefed American scientists on British developments.[58] He discovered that the American S-1 Project (later renamed the Manhattan Project) was smaller than the British, and not as far advanced.[54] The British and American projects exchanged information, but did not initially combine their efforts. British officials did not reply to an August 1941 American offer to create a combined project.[59] In November 1941, Frederick L. Hovde, the head of the London liaison office of the American Office of Scientific Research and Development (OSRD), raised the issue of cooperation and exchange of information with Anderson and Lord Cherwell, who demurred, ostensibly over concerns about American security. Ironically, it was the British project that had already been penetrated by atomic spies for the Soviet Union.[60]

The United Kingdom did not have the manpower or resources of the United States, and despite its early and promising start, Tube Alloys fell behind its American counterpart and was dwarfed by it.[61] On 30 July 1942, Anderson advised the Prime Minister, Winston Churchill, that: "We must face the fact that ... [our] pioneering work ... is a dwindling asset and that, unless we capitalise it quickly, we shall be outstripped. We now have a real contribution to make to a 'merger.' Soon we shall have little or none."[62]

The British considered producing an atomic bomb without American help, but it would require overwhelming priority, disruption to other wartime projects was inevitable, and it was unlikely to be ready in time to affect the outcome of the war in Europe. The unanimous response was that before embarking on this, another effort should be made to secure American cooperation.[63] At the Quebec Conference in August 1943, Churchill and the President of the United States, Franklin Roosevelt, signed the Quebec Agreement, which merged the two national projects.[64] The Quebec Agreement established the Combined Policy Committee and the Combined Development Trust to coordinate their efforts, and that the weapons could only be used if both the USA and UK governments agreed.[65] The 19 September 1944 Hyde Park Agreement extended both commercial and military cooperation into the post-war period.[66]

End of American cooperation

President Harry Truman and prime ministers Clement Attlee and Mackenzie King boarding USS Sequoia for discussions about nuclear weapons, November 1945

With the end of the war, the Special Relationship between Britain and the United States "became very much less special".[67] The British government had trusted that America would share nuclear technology, which it considered a joint discovery.[68] On 8 August 1945 the Prime Minister, Clement Attlee, sent a message to President Harry Truman in which he referred to themselves as "heads of the Governments which have control of this great force".[68] But Roosevelt had died on 12 April 1945, and the Hyde Park Agreement was not binding on subsequent administrations.[69] In fact, it was physically lost. When Wilson raised the matter in a Combined Policy Committee meeting in June, the American copy could not be found.[70]

On 9 November 1945, Attlee and the Prime Minister of Canada, Mackenzie King, went to Washington, D.C., to confer with Truman about future cooperation in nuclear weapons and nuclear power.[71][72] A Memorandum of Intention they signed replaced the Quebec Agreement. It made Canada a full partner, continued the Combined Policy Committee and Combined Development Trust, and reduced the obligation to obtain consent for the use of nuclear weapons to merely requiring consultation.[73] The three leaders agreed that there would be full and effective cooperation on atomic energy, but British hopes were soon disappointed;[74] the Americans restricted cooperation to basic scientific research.[75]

The next meeting of the Combined Policy Committee on 15 April 1946 produced no accord on collaboration, and resulted in an exchange of cables between Truman and Attlee. Truman cabled on 20 April that he did not see the communiqué he had signed as obligating the United States to assist Britain in designing, constructing and operating an atomic energy plant.[76] The passing of the Atomic Energy Act of 1946 (McMahon Act) in August 1946, which was signed by Truman on 1 August 1946, and went into effect at midnight on 1 January 1947,[77] ended technical cooperation. Its control of "restricted data" prevented the United States' allies from receiving any information.[78]

This partly resulted from the arrest for espionage of British physicist Alan Nunn May, who had worked in the Montreal Laboratory, in February 1946, while the legislation was being debated.[79] It was but the first of a series of spy scandals. The arrest of Klaus Fuchs in January 1950,[80] and the June 1951 defection of Donald Maclean, who had served as a British member of the Combined Policy Committee from January 1947 to August 1948, left Americans with a distrust of British security arrangements.[81] The remaining British scientists working in the United States were denied access to papers that they had written just days before.[82]

Resumption of independent UK efforts

Attlee set up a cabinet sub-committee, the Gen 75 Committee (known informally by Attlee as the "Atomic Bomb Committee"),[83] on 10 August 1945 to examine the feasibility of an independent British nuclear weapons programme.[84] The Chiefs of Staff Committee considered the issue of nuclear weapons in July 1946, and recommended that Britain acquire them.[85] The Chief of the Air Staff, Lord Tedder, officially requested an atomic bomb in 9 August 1946.[86][87] The Chiefs of Staff estimated that 200 bombs would be required by 1957.[88] A nuclear reactor and plutonium-processing facility was approved by the Gen 75 committee on 18 December 1945 "with the highest urgency and importance".[89]

Head and shoulders of man in suit and tie
William Penney, Chief Superintendent Armament Research, was in charge of atomic bomb development

The Tube Alloys Directorate was transferred from the Department of Scientific and Industrial Research to the Ministry of Supply effective 1 November 1945.[90] To coordinate the atomic energy effort, Marshal of the Royal Air Force Lord Portal, the wartime Chief of the Air Staff, was appointed the Controller of Production, Atomic Energy (CPAE) in March 1946.[91] The Gen 75 Committee considered the proposal in October 1946.[92] In October 1946, Attlee called a meeting to discuss building a gaseous diffusion plant for uranium enrichment. Michael Perrin, who was present, later recalled that:

The meeting was about to decide against it on grounds of cost, when [Ernest] Bevin arrived late and said "We've got to have this thing. I don't mind it for myself, but I don't want any other Foreign Secretary of this country to be talked at or to by the Secretary of State of the United States as I have just been in my discussion with Mr Byrnes. We've got to have this thing over here, whatever it costs ... We've got to have the bloody Union Jack flying on top of it."[84][93]

The decision to proceed was formally made on 8 January 1947 at a meeting of Gen 163, a subcommittee of the Gen 75 Committee consisting of six Cabinet members, including Attlee,[94] and was publicly announced in the House of Commons on 12 May 1948. D notice No. 25 prohibited the publication of details on the design, construction or location of atomic weapons.[95][96] The project was given the cover name "High Explosive Research".[97]

Production facilities were constructed under the direction of Christopher Hinton, who established his headquarters in a former Royal Ordnance Factory at Risley in Lancashire.[98] These included a uranium metal plant at Springfields,[99] nuclear reactors and a plutonium processing plant at Windscale,[100] and a gaseous diffusion uranium enrichment facility at Capenhurst, near Chester.[101] The two Windscale reactors became operational in October 1950 and June 1951.[102] The gaseous diffusion plant at Capenhurst began producing highly enriched uranium in 1954.[103] Uranium ore was stockpiled at Springfields. As the American nuclear programme expanded, its requirements became greater than the production of the existing mines. To gain access to the stockpile, they reopened negotiations in 1947. This resulted in the 1948 Modus Vivendi,[104] which allowed for consultation on the use of nuclear weapons, and limited sharing of technical information between the United States, Britain and Canada.[105][106] In the meantime, nuclear deterrence was provided by the United States Strategic Air Command,[107] which had begun operating from British bases in 1949.[108]

As Chief Superintendent Armament Research (CSAR, pronounced "Caesar"), Penney directed bomb design from Fort Halstead.[109] In 1951 his design group moved to a new site at Aldermaston in Berkshire.[110]

Unsuccessful attempt to renew American partnership

By 1949, international control of atomic weapons seemed almost impossible to achieve, and Truman proposed to the Joint Committee on Atomic Energy in July a "full partnership" with Britain in exchange for uranium; negotiations between the two countries began that month. While the first Soviet atomic bomb test in August 1949 was embarrassing to the British (who had not expected a Soviet atomic weapon until 1954) for having been beaten, it was for the Americans another reason for cooperation. Although they would soon have their own nuclear capability, the British proposed that instead of building their own uranium-enrichment plant they would send most of their scientists to work in the US, as well as plutonium from Windscale. While Britain would not formally give up building or researching its own weapons, the United States would manufacture all bombs and allocate some to Britain.[111][112][113]

By agreeing to subsume its own weapons program within the Americans', the plan would have given Britain nuclear weapons much sooner than its own target date of late 1952. Although a majority of Americans including Truman supported the proposal, several key officials, including the Atomic Energy Commission's Lewis Strauss and Senator Arthur Vandenberg, did not. Their opposition, and security concerns caused by the arrest in early 1950 of Klaus Fuchs, a Soviet spy working at Harwell, ended the negotiations in January 1950.[112] After Britain developed atomic weapons through its own efforts, the scientist Sir Leonard Owen nonetheless stated that "the McMahon Act was probably one of the best things that happened ... as it made us work and think for ourselves along independent lines."[114]

First test and early systems

HMS Plym in 1943.
The UK's first nuclear test, Operation Hurricane, in 1952.
File:Blue Danube Bomb.jpg
A Blue Danube bomb. The first Blue Danube weapons issued to the RAF were of 10–12-kiloton-of-TNT (42–50 TJ) yield, approximately the same yield as the Hiroshima bomb, although Blue Danube was of the implosion type similar to the Nagasaki bomb. This airframe design was used for all the devices detonated at Christmas Island in the Operation Grapple tests.

Churchill, now again prime minister, announced on 17 February 1952 that the first British weapon test would occur before the end of the year. Operation Hurricane was detonated in the frigate HMS Plym anchored in the Monte Bello Islands, Western Australia on 3 October 1952.[114] This led to the first deployed weapon, the Blue Danube free-fall bomb, in November 1953. It was very similar to the American Mark 4 weapon in having a 60-inch (1,500 mm) diameter, 32 lens implosion system with a levitated core suspended within a natural uranium tamper. The warhead was contained within a bomb casing measuring 62 inches (1.6 m) diameter and 24 feet (7.3 m) long, and being so large, could only be carried by the V bomber fleet. Britain thereby became the third country to test nuclear weapons.[115] The first Blue Danube atomic bombs were delivered to Bomber Command in November 1953,[116] although the V bombers to deliver them were not available until 1955.[117][118]

A nuclear landmine dubbed Brown Bunny, later Blue Bunny, and finally Blue Peacock that used the Blue Danube warhead was developed from 1954 with the goal of deployment in the Rhine area of Germany. The system would have been set to an eight-day timer in the case of invasion of Western Europe by the Soviets but was cancelled in February 1958 with only two built. It was judged that the risks posed by the nuclear fallout and the political aspects of preparing for destruction and contamination of allied territory were too high to justify. Another reason for cancellation revealed by numerous archived declassified documents was that the Army felt it was too unwieldy and diverted their efforts into a successor, Violet Vision, based on the smaller successor to Blue Danube, Red Beard. None were ever built, the Army instead receiving US ADMs or Atomic Demolition Munitions under the established procedures for supply of NATO allies from US stocks held in US custody in Europe. A sea mine based on the Blue Danube warhead and codenamed Cudgel was also envisaged for delivery by midget submarines, referred to by naval sources as "sneak craft"; perhaps reflecting a belief that these craft were really rather ungentlemanly methods of waging war. None were built.

A gaseous diffusion plant was built at Capenhurst, near Chester and started production in 1953 producing low enriched uranium (LEU). By 1957 it was capable of annually producing 125 kg of highly enriched uranium (HEU). The capacity was further increased and by 1959 it may have been producing as much as 1600 kg per year.[119] At the end of 1961, having produced between 3.8 and 4.9 tonnes of HEU it was switched over to LEU production for civil use. Additional plutonium production was provided by eight electricity generating Magnox reactors at Calder Hall and Chapelcross which started operating in 1956 and 1959 respectively.

Thermonuclear weaponry

File:Blue Danube release from Valiant bomber.jpg
A Blue Danube bomb released from a Valiant bomber. The fins are not yet extended to quickly stabilise the bomb into a predictable ballistic trajectory. Fuzing was by means of a barometric 'gate' to switch on the radar altimeter controlled firing circuit. These bomb casings were used for all the air-drop tests at Christmas Island and Maralinga, Australia. Detonation was approximately 52 seconds after release from the aircraft.


A month after Britain's first atomic weapons test, America tested the first thermonuclear (hydrogen) bomb. The Soviets tested their first in 1953. Penney believed that Britain could not afford to develop a hydrogen bomb.[25] Henry Tizard believed that the nation should focus on conventional forces instead of duplicating the nuclear capabilities of the American Strategic Air Command, which already defended Britain and Europe:[120]: 86–87  "We are a great nation, but if we continue to behave like a Great Power we shall soon cease to be a great nation. Let us take warning from the fate of the Great Powers of the past and not burst ourselves with pride."[120]: 86–87 

First Sea Lord Lord Mountbatten and Chief of the Imperial General Staff Gerald Templer supported the development of a hydrogen bomb, but preferred more support for conventional forces. They believed that the large American and Soviet nuclear forces acted as mutual deterrents for nuclear war, making conventional war more likely.[121]: 145–147  Others proposed that, instead of repeated unsuccessful attempts to increase cooperation with the Americans, Britain work with Australia, Canada, and other Commonwealth countries. (Britain could not disclose atomic information to Australia despite testing weapons there because of restrictions in existing agreements with the United States.)[120]: 162–163 

The Chiefs of Staff Committee and the Churchill ministry, however, believed that

If we did not develop megaton weapons we would sacrifice immediately and in perpetuity our position as a firstclass power. We would have to rely on the whim of the United States for the effectiveness of the whole basis of our strategy.[122]

The government decided on 27 July 1954 to begin development of a thermonuclear bomb and announced its plans in February 1955.[123]

An independent deterrent

Believing that the United Kingdom was extremely vulnerable to a nuclear attack to which defence was impossible, the Chiefs of Staff and the RAF first advocated a British nuclear deterrence—not just nuclear weapons—in 1945: "It is our opinion that our only chance of securing a quick decision is by launching a devastating attack upon [enemy cities] with absolute weapons." In 1947 the Chiefs of Staff stated that even with American help the United Kingdom could not prevent the "vastly superior" Soviet forces from overrunning Western Europe, from which Russia could destroy Britain with missiles without using atomic weapons. Only "the threat of large-scale damage from similar weapons" could prevent the Soviet Union from using atomic weapons in a war.[120]: 48, 397–398 

John Slessor, who became Chief of the Air Staff in 1950, wrote that year that the Soviet superiority in European forces was so great that even "an ultimatum by Russia within the next two to three years" might cause Western Europe to surrender without a war. He feared that the United Kingdom might also do so "unless we can make ourselves far less defenceless than we are now." By 1952 the Air Ministry had abandoned the concept of a conventional defense of Western Europe.[121]: 71, 78–79  The hydrogen bomb increased the threat to Britain. In 1957, a government study stated that although RAF fighters would "unquestionably be able to take a heavy toll of enemy bombers, a proportion would inevitably get through. Even if it were only a dozen, they could with megaton bombs inflict widespread devastation." Although disarmament remained a British goal, "the only existing safeguard against major aggression is the power to threaten retaliation with nuclear weapons."[120]: 429–430 

Churchill stated in a 1955 speech that deterrence would be "the parents of disarmament" and that, unless Britain contributed to Western deterrence with its own weapons, during a war the targets that threatened it the most might not be prioritized. Harold Macmillan stated that nuclear weapons would give Britain influence over targeting and American policy, and would affect strategy in the Middle East and Far East. Duncan Sandys stated that nuclear weapons reduced Britain's dependence on the United States.[124] The Suez Crisis increased the value to Britain of a deterrent that would give it greater influence with the US and USSR.[125]

Independent targeting was also vital. The Chiefs of Staff believed that—contrary to Tizard's view—once the USSR became able to attack the United States itself with nuclear weapons in the late 1950s, America might not risk its own cities to defend Europe, or not emphasize targets that endangered the United Kingdom more than the United States:[120]: 185–187 [126]

When New York is vulnerable to attack the United States will not use her strategic weapon in defence of London. The United Kingdom must, therefore, have its own retaliatory defence. Similarly, however, we will not be prepared to sacrifice the United Kingdom in the defence of say Darwin, and eventually each political unit must have its own means of retaliation.[120]: 416 

Britain thus needed the ability to convince the USSR that attacking Europe would be too costly regardless of American participation. Part of the perceived effectiveness of an independent deterrent was the willingness to target enemy cities. Slessor saw atomic weapons as a way to avoid a third devastating world war given that the two previous ones had begun without them. While he sought to deemphasize city targeting in British plans as Air Chief,[120]: 110–112, 114  Slessor wrote in 1954 after retirement:[126]

And if [war] is forced upon us, we must be able to instantly deliver a crushing counter attack upon aggression at its source—not merely at its airfields, its launching sites and submarine bases, at its armies in the field but at the heart of the aggressor country. There will be the battlefield if battlefield there must be.[126]

When Nigel Mills became head of RAF Bomber Command in 1955 he similarly insisted on targeting Soviet cities, writing "Whoever would be afraid of launching a sudden attack if he thought the greater part of our retaliation would come back to his airfields?"[127] The belief in the importance of retaining an independent capability has continued over several decades and changes in government. As the Defence Council stated in 1980,[8]

our force has to be visibly capable of making a massive strike on its own ... We need to convince Soviet leaders that even if they thought ... the US would hold back, the British force could still inflict a blow so destructive that the penalty for aggression would have proved too high.[8]

There was little dissent in the House of Commons; nuclear weapons had almost bipartisan support until 1960, with only the Liberals dissenting in 1958. Despite opposition from its left wing the Labour party supported British nuclear weapons but opposed tests, and Labour Opposition Leader Hugh Gaitskell and shadow foreign secretary Aneurin Bevan agreed with Sandys on the importance of reducing dependence on the American deterrent. The left-wing Bevan told his colleagues that their demand for unilateral nuclear disarmament would send a future Labour government "naked into the conference chamber" during international negotiations.[125] The Manchester Guardian and other newspapers critical of the Conservative government supported the British deterrent, although the Guardian did criticise the government for relying on developing bombers rather than missiles to carry the weapons.[128] In 1962 it stated that the forthcoming Chinese nuclear weapon was a reason for having more than one Western nuclear nation. From 1955 the government chose to emphasize the nuclear deterrent and de-emphasize conventional forces.[125] The Economist, the New Statesman, and many left-wing newspapers supported the reliance on nuclear deterrence and nuclear weapons, but in their view considered that of the United States would suffice, and that of the costs of the "nuclear umbrella" was best left to be borne by the United States alone.[129]

Renewed American partnership

A Yellow Sun thermonuclear bomb

File:1957-06-03 British H-Bomb (claimed).ogv The first prototype, Short Granite, was detonated on 15 May 1957 in Operation Grapple, with disappointing results at 300 kilotons of TNT (1.3 PJ), when the target requirement was 1 Mt (4.2 PJ). A further test of Purple Granite yielded less at 200 kt (0.84 PJ). An interim weapon was deployed in the V-bomber fleet until a true thermonuclear weapon could be devised from the Christmas Island tests. This interim weapon was never tested; it was a very large unboosted pure fission weapon estimated to yield 400 kt (1.7 PJ). It was derived from the Orange Herald warhead tested on 31 May 1957 yielding 720 kt (3.0 PJ)[130] known as Green Grass.

After British scientists demonstrated to the United States in late 1957 that they had developed a Teller-Ulam design different from American methods and thus understood how to build a hydrogen bomb, the 1958 US-UK Mutual Defence Agreement made fully developed and tested American designs available more quickly and more cheaply. The first of these was the US B28 nuclear bomb, which was anglicised and manufactured in the UK as Red Snow and quickly deployed as Yellow Sun Mk.2 in the V-bomber fleet. Red Snow became the warhead of choice for the Blue Steel stand-off missile and some of the Skybolt missiles intended for carriage by the V-bombers. (The American B28 design had reliability issues. The British soon withdrew their warheads from deployment, and never again simply copied an American design.)[25] Under the Mutual Defence Agreement 5.4 tonnes of UK produced plutonium was sent to the US in return for 6.7 kg of tritium and 7.5 tonnes of HEU over the period 1960–1979, replacing Capenhurst production, although much of the HEU was used not for weapons, but as fuel for the growing UK fleet of nuclear submarines, both of the Polaris variety and others numbering approx twelve.

Fifty-eight Blue Danube bombs were produced, although archived declassified files indicate that only a small proportion of these were ever serviceable at any one time. It remained in service until 1963, when it was replaced by Red Beard, a smaller tactical boosted fission weapon that used the same fissile core as Blue Danube and was deployed on many smaller aircraft than the V-bombers, both ashore and at sea aboard five carriers. Stocks of Red Beard were maintained in Cyprus, Singapore, and a smaller number in the UK.

It was the largest pure fission weapon ever deployed by any nuclear state. Green Grass was deployed first in a modified Blue Danube casing and known as Violet Club. A later variant was deployed in a Yellow Sun Mk.1 casing.

In 1960 the government cancelled the Blue Streak missile based on the Chiefs of Staff's conclusion that it was too vulnerable to attack and thus was only useful for a first strike and decided to purchase the American Skybolt missile instead.[120]: 286–288  In 1962 it cancelled the Blue Steel extended range upgrade (Blue Steel Mk2) for Skybolt. Similarly, reassessments of Soviet capabilities changed military perceptions and led to the removal of Thor IRBM missiles in the UK; and Jupiter IRBMs in Italy and Turkey; although the Turkish sites were implicated in an alleged deal following the Cuban Missile Crisis. To consternation, and considerable protests, the incoming Kennedy administration cancelled Skybolt at the end of 1962 because it was believed by the US Secretary of State for Defense, Robert McNamara, that other delivery systems were progressing better than expected, and a further expensive system was surplus to US requirements.

End of cross-party support

Gaitskell's Labour party ceased supporting an independent deterrent in 1960 via its new "Policy for Peace", after the cancellation of Blue Streak made nuclear independence less likely. Labour also adopted a resolution favoring unilateral disarmament. Although Gaitskell opposed the resolution and it was reversed in 1961 in favor of continuing support of a general Western nuclear deterrent, the party's opposition to a British deterrent remained and became more prominent. This became a campaign issue during the 1964 general election. Alec Douglas-Home's incumbent Conservatives stated that the British deterrent was both necessary for independence from the Americans and maintaining British world influence, and was "working for peace" in such cases as the passage of the Nuclear Test Ban Treaty. Led by Gaitskell's successor Harold Wilson, Labour emphasized domestic economic issues but called deterrence the "Tory Nuclear Pretense" which would be neither independent nor effective. The populace's greater interest in domestic over foreign policy likely contributed to Labour's victory.[125]

The Polaris A1 or A2 missile, seen here on a launch pad in Cape Canaveral, was a submarine-launched ballistic missile purchased from the US. The UK purchased the A3T variant, the final production model, that incorporated hardened missile electronic components to resist ABM attack in the boost phase, although neither the three re-entry vehicles or UK-manufactured warheads were hardened, leading to the Chevaline programme.


After the cancellation of Skybolt, the UK purchased Polaris missiles for use in UK-built ballistic missile submarines. The agreement between US President John F. Kennedy and Prime Minister of the United Kingdom Harold Macmillan, the Polaris Sales Agreement, was announced on 21 December 1962 and HMS Resolution made her first Polaris-armed operational patrol on 15 June 1968.[131] In the 1970s the UK Polaris RVs and warheads were vulnerable to the Soviet ABM screen concentrated around Moscow, and the UK developed a Polaris improved-front-end (IFE) codenamed Chevaline, designed to counter this ABM defence which threatened to completely nullify an independent UK deterrent posture. When Chevaline became public knowledge in 1980, it generated huge controversy as it had been kept secret by the four governments of Wilson, Heath, Wilson (again) and Callaghan, whilst costs rocketed during a period of high inflation, until disclosed by the Thatcher government. By the time it entered service in 1982 it had cost approx £1bn. The final Polaris/Chevaline patrol took place in 1996, two years after the first Trident-carrying submarine sailed on its first patrol.

As well as the establishment at Aldermaston, the UK nuclear weapons programme also has a factory at Burghfield nearby which assembled the weapons and is responsible for their maintenance, and had another in Cardiff which fabricated non-fissile components and a 2000-acre (8 km²) test range at Foulness. Since 1993 the sites have been managed by private consortia. The Foulness and Cardiff facilities closed in October 1996 and February 1997 respectively.

Current weapons programmes


HMS Vanguard, one of four Vanguard class ballistic missile submarines of the Royal Navy, which serve as the UK's nuclear delivery system.
Rare WE.177A sectioned instructional example of an operational round, one of only two in existence at the Boscombe Down Aviation Collection

The UK currently has four Vanguard-class submarines based at HMNB Clyde in Scotland, armed with nuclear-tipped Trident missiles. The principle of operation is based on maintaining deterrent effect by always having at least one submarine at sea, and was designed for the Cold War period. One submarine is normally undergoing maintenance and the remaining two in port or on training exercises.

Each submarine carries 16 Trident II D-5 missiles, which can each carry up to 12 warheads. However, the UK government announced in 1998 that each submarine would carry only 48 warheads, an increase of 50% over the 32 warheads carried by Trident's predecessor, Chevaline, (halving the limit specified by the previous government), which is an average of three per missile. However one or two missiles per submarine are probably armed with fewer warheads for "sub-strategic" use causing others to be armed with more; but this is speculative.

The UK-designed warheads are thought to be selectable between 0.3, 5–10 and 100 kt (1.3, 21–42 and 420 TJ)[citation needed]; the yields obtained using either the unboosted primary, the boosted primary, or the entire "physics package"; these yields and similar data are speculative. Although the UK designed, manufactured and owns the warheads, there is evidence that the warhead design is similar to, or even based on, the US W76 warhead fitted in some US Navy Trident missiles, with design data being supplied by the United States through the 1958 US-UK Mutual Defence Agreement.[132][133] The United Kingdom owns 58 missiles which are shared in a joint pool with the United States government and these are exchanged when requiring maintenance with missiles from the United States Navy's own pool and vice versa.[134][135] Some non-nuclear components for the British nuclear warhead are procured from the U.S. for reasons of cost effectiveness.[136]

Trident renewal

A decision on the renewal of Trident was made on 4 December 2006. Prime Minister Tony Blair told MPs it would be "unwise and dangerous" for the UK to give up its nuclear weapons. He outlined plans to spend up to £20bn on a new generation of submarines for Trident missiles. He said submarine numbers may be cut from four to three, while the number of nuclear warheads would be cut by 20% to 160. Blair said although the Cold War had ended, the UK needed nuclear weapons, as no-one could be sure another nuclear threat would not emerge in the future.

The 2010 coalition government agreed "that the renewal of Trident should be scrutinised to ensure value for money. Liberal Democrats will continue to make the case for alternatives." Research and development work continued with an 'Initial Gate' procurement decision, but the 'Main Gate' decision to manufacture a replacement was rescheduled for 2016, after the next election.[137] A vote in the House of Commons on whether to replace the existing four Vanguard-class submarines was scheduled for 18 July 2016.[138]

That vote on the so-called Trident renewal programme motion was held on that date[139] and it passed with a significant majority with 472 MPs voting in favour and 117 against. (As expected, Jeremy Corbyn and 47 Labour MPs had voted against it; 41 did not vote but 140 Labour votes were cast in favour of the motion.[140]) The new Dreadnought-class submarines were expected to come into operation by 2028[141] according to some estimates and certainly by the 2030s,[142] extending the programme's life until at least the 2060s.[143] At that time, there was already some urgency to move ahead because some experts predicted it could take 17 years to develop the replacement for the Vanguard-class submarines [144][145] The new class would continue to carry the Trident D-5 missiles.[146]

Deployment of US tactical nuclear weapons

Until 1992 UK forces also deployed US tactical nuclear weapons as part of a US-UK dual-key NATO nuclear sharing role.[147][148] This arrangement commenced in 1958 as Project E to provide nuclear weapons to the RAF prior to a sufficient number of Britain's own nuclear weapons becoming available.

The weapons deployed included nuclear artillery, nuclear demolition mines and warheads for Corporal and Lance missiles in Germany; theatre nuclear weapons on RAF aircraft;[149] Mark 101 nuclear depth bombs on RAF Shackleton maritime patrol aircraft, later replaced by a modern successor, the B-57 deployed on RAF Nimrod aircraft.

The Lance missiles were purchased in 1975,[150] to replace Honest John missiles which had been bought in 1960;[151][152] and were themselves a replacement for the US Corporal missiles deployed in Germany by the Royal Artillery. Not generally recognised is the fact that the Royal Artillery deployed a numerically greater quantity of US nuclear weapons than the RAF and Royal Navy combined, peaking at 277 in 1976–78; with a further 50 ADMs deployed with another British Army unit, the Royal Engineers, peaking in 1971–81.[153] The dual-key agreement for controlling US tactical nuclear weapons, known as the Heidelberg Agreement, was made on 30 August 1961. The UK sponsored access for the Canadian Army Honest John missile deployments to the US/UK nuclear warhead storage sites.[154]

During the 1980s nuclear armed USAF Ground Launched Cruise Missiles were deployed at RAF Greenham Common and RAF Molesworth. Until about 2006 the US continued to store nuclear weapons in the UK, when approximately 110 tactical B61 nuclear bombs stored at RAF Lakenheath for deployment by USAF F-15E Strike Eagle aircraft were removed.[155][156]

The UK continues to permit the US to deploy nuclear weapons from its territory, the first having arrived in 1954.[157]

Research and development facilities

Atomic Weapons Establishment, Aldermaston

The Atomic Weapons Establishment (AWE), Aldermaston (formerly the Atomic Weapons Research Establishment, Aldermaston) is situated just 7 miles (11 km) north of Basingstoke and approximately 14 miles (23 km) south-west of Reading, Berkshire, near a village called Aldermaston, bordering with Tadley. It was built in 1949 on the site of a former World War II Royal Air Force base and converted to nuclear weapons research, design and development in the 1950s. Although some early test devices were probably assembled on this site, final assembly of Service-engineered weapons takes place at the nearby site of Burghfield.

Royal Ordnance Factories, Cardiff and Burghfield

Other nuclear weapons sites could be found in Cardiff and Burghfield near Reading, Berkshire. These were the only two Royal Ordnance Factories (ROFs) not privatised in the 1980s.

ROF Cardiff, which closed in 1997, had been involved in nuclear weapons programmes since 1961. The site was used for the task of recycling old nuclear weapons and precisely shaping uranium 235 (U235) and metallic beryllium components for the boosted fission devices used as primaries or 'triggers' in modern thermonuclear weapons.[158] ROF Burghfield was a former Filling Factory, opened in 1942, and run as an Agency Factory, by Imperial Tobacco, to fill Oerlikon 20 mm ammunition.[159]

Nuclear warheads from the Trident missiles are transported by road convoy several times a year from Coulport to Burghfield for refurbishment. Between 2000 and 2016 there were 180 accidents involving the vehicles, ranging from minor traffic accidents to a sudden total loss of power in one of the 44-tonne lorries that halted a convoy and caused a double lane closure and a tailback on the M6 motorway. The accidents have been more frequent in recent years.[160]

Politics, decision making and nuclear posture

Anti-nuclear movement

The now-familiar peace symbol was originally the Campaign for Nuclear Disarmament logo.

The anti-nuclear movement in the United Kingdom consists of groups who oppose nuclear technologies such as nuclear power and nuclear weapons. Many different groups and individuals have been involved in anti-nuclear demonstrations and protests over the years.

One of the most prominent anti-nuclear groups in the UK is the Campaign for Nuclear Disarmament (CND). CND's Aldermaston Marches began in 1958 and continued into the late 1960s when tens of thousands of people took part in the four-day marches. One significant anti-nuclear mobilisation in the 1980s was the Greenham Common Women's Peace Camp. In London, in October 1983, more than 300,000 people assembled in Hyde Park as part of the largest protest against nuclear weapons in British history. In 2005 in Britain, there were many protests about the government's proposal to replace the ageing Trident weapons system with a newer model.

Nuclear posture

UK nuclear posture during the Cold War was informed by dependence on the United States. Operational control of the UK Polaris force was assigned to SACLANT, while targeting policy for its missiles was determined, as for the V-bomber force before it, by NATO's SACEUR, while maintaining an independent wholly UK targeting policy for circumstances when a critical national emergency required it to be used alone, without the UK's NATO allies.[161][162] In these circumstances, the Moscow criterion referred to the ability of the UK to strike back at the highly centralised Soviet decision-making apparatus concentrated in the Moscow area, intended to destroy the ability of the Soviet leadership to remain in control of a Soviet Union otherwise untouched. The early beginnings of studies to increase the likelihood of successful penetration of the Polaris warheads to Moscow can be traced back to 1964,[163] before the Polaris system was deployed, in order to preserve this capability in the face of anti-ballistic missile batteries around Moscow. These studies later materialised as Chevaline.[164][165]

The UK has relaxed its nuclear posture since the collapse of the Soviet Union. The Labour government's 1998 Strategic Defence Review made reductions from the plans announced by the previous Conservative government:[166]

  • The stockpile of "operationally available warheads" was reduced from 300 to "less than 200"
  • The final batch of missile bodies would not be purchased, limiting the fleet to 58.
  • A submarine's load of warheads were reduced from 96 to 48. This reduced the explosive power of the warheads on a Vanguard class Trident submarine to "one third less than a Polaris submarine armed with Chevaline." However 48 warheads per Trident submarine represents a 50% increase on the 32 warheads per submarine of Chevaline. Total explosive power has been in decline for decades as the accuracy of missiles has improved, therefore requiring less power to destroy each target. Trident can destroy 48 targets per submarine, as opposed to 32 targets that could be destroyed by Chevaline.
  • Submarines' missiles would not be targeted, but rather at several days "notice to fire".
  • Although one submarine would always be on patrol it will operate on a "reduced day-to-day alert state". A major factor in maintaining a constant patrol is to avoid "misunderstanding or escalation if a Trident submarine were to sail during a period of crisis."

Current UK posture as outlined in the Strategic Defence Review of 1998[167] is as it has been for many years; Trident SLBMs still provide the long-range strategic element. Until 1998 the aircraft-delivered, free-fall WE.177A, WE.177B and WE.177C bombs provided a sub-strategic option in addition to their designed function of tactical battlefield weapons. With the retirement of WE.177, a sub-strategic warhead is to be used with some (but not all) deployed Trident missiles. The exact mix of warheads is unknown, as are their number and yield.[citation needed] The 2010 Strategic Defence and Security Review further pledged to reduce its requirement for operationally available warheads from fewer than 160 to no more than 120.[168] In a January 2015 written statement, Defence Secretary Michael Fallon reported that " All Vanguard Class SSBNs on continuous at-sea deterrent patrol now carry 40 nuclear warheads and no more than eight operational missiles".[169] In April 2017 Defence Secretary Michael Fallon confirmed that the UK would use nuclear weapons in a "pre-emptive initial strike" in "the most extreme circumstances".[170]

Nuclear weapons control

The precise details of how a British Prime Minister would authorise a nuclear strike remain secret, although the principles of the Trident missile control system is believed to be based on the plan set up for Polaris in 1968, which has now been declassified. A closed-circuit television system was set up between 10 Downing Street and the SSBN Control Officer at the Northwood Headquarters of the Royal Navy. Both the Prime Minister and the SSBN Control Officer would be able to see each other on their monitors when the command was given. If the link failed – for instance during a nuclear attack or when the PM was away from Downing Street – the Prime Minister would send an authentication code which could be verified at Northwood. The PM would then broadcast a firing order to the SSBN submarines via the Very Low Frequency radio station at Rugby. The UK has not deployed control equipment requiring codes to be sent before weapons can be used, such as the U.S. Permissive Action Link, which if installed would preclude the possibility that military officers could launch British nuclear weapons without authorisation.

WE.177 safety and arming keys

Until 1998, when it was withdrawn from service, the WE.177 bomb was armed with a standard tubular pin tumbler lock (as used on bicycle locks) and a standard allen key was used to set yield and burst height. Currently, British Trident missile commanders are able to launch their missiles without authorisation, whereas their American counterparts cannot. At the end of the Cold War the U.S. Fail Safe Commission recommended installing devices to prevent rogue commanders persuading their crews to launch unauthorised nuclear attacks. This was endorsed by the Nuclear Posture Review and Trident missile Coded Control Devices were fitted to all U.S. SSBNs by 1997. These devices prevented an attack until a launch code had been sent by the Chiefs of Staff on behalf of the President. The UK took a decision not to install Trident CCDs or their equivalent on the grounds that an aggressor might be able to wipe out the British chain of command before a launch order had been sent.[171][172][173]

In December 2008 BBC Radio 4 made a programme titled The Human Button, providing new information on the manner in which the United Kingdom could launch its nuclear weapons, particularly relating to safeguards against a rogue launch. Former Chief of the Defence Staff (most senior officer of all British armed forces) and Chief of the General Staff (most senior officer in the British Army), General Lord Guthrie of Craigiebank, explained that the highest level of safeguard was against a prime minister ordering a launch without due cause: Lord Guthrie stated that the constitutional structure of the United Kingdom provided some protection against such an occurrence, as while the Prime Minister is the chief executive and so practically commands the armed services, the formal commander-in-chief is the Monarch (to whom they swear allegiance to and indeed, is called the "Royal" Navy/Air Force), to whom the chief of the defence staff could appeal: "the chief of the defence staff, if he really did think the prime minister had gone mad, would make quite sure that that order was not obeyed... You have to remember that actually prime ministers give direction, they tell the chief of the defence staff what they want, but it's not prime ministers who actually tell a sailor to press a button in the middle of the Atlantic. The armed forces are loyal, and we live in a democracy, but actually their ultimate authority is the Queen."[174]

Photograph of a hand holding a pistol grip; the grip has a red trigger button and a coiled cable connected to its base.
Weapons Engineer Officers Tactical Trigger used to launch a Trident Missile. Taken in 2012 aboard HMS Vigilant during a test launch of an unarmed Trident ballistic missile at sea.

The same interview pointed out that while the Prime Minister would have the constitutional authority to fire the Chief of the Defence Staff, he could not appoint a replacement as the position is appointed by the monarch. During the Cold War the Prime Minister was also required to name a senior member of the cabinet as his/her designated survivor, who would have the authority to order a nuclear response in the event of an attack incapacitating the Prime Minister, and this system was re-adopted after the September 11 attacks.

The programme also addressed the workings of the system; detailing that two persons are required to authenticate each stage of the process before launching, with the submarine captain only able to access the firing trigger after two safes have been opened with keys held by the ship's executive and weapons engineering officers. It was explained that all Prime Ministers issue hand-written orders, termed the letters of last resort,[175] seen by their eyes only, sealed and stored within the safes of each of the four Royal Navy Vanguard class submarines. These notes instruct the submarine commander of what action to take in the event of the United Kingdom being attacked with nuclear weapons that destroy Her Majesty's Government in the United Kingdom and/or the chain of command.

Although the final orders of the Prime Minister are at his or her discretion, and no fixed options exist, according to the December 2008 BBC Radio 4 documentary The Human Button there were four known options: retaliating with nuclear weapons, not retaliating with nuclear weapons, the submarine commander uses his own judgement, or the submarine commander places himself under United States or Australian command if possible. This system of issuing notes containing orders in the event of the head of government's death is said to be unique to the United Kingdom (although the concept of written last orders, particularly of a ship's captain, is a naval tradition), with other nuclear powers using different procedures. The letters are destroyed unopened whenever a Prime Minister leaves office.

All relevant former prime ministers have supported an "independent nuclear deterrent", including David Cameron[176] and the incumbent Prime Minister Theresa May.[177] Only one former Prime Minister, Lord Callaghan, has given any insight on his orders: Callaghan stated that, although in a situation where nuclear weapon use was required – and thus the whole purpose and value of the weapon as a deterrent had failed – he would have ordered use of nuclear weapons, if needed: ...if we had got to that point, where it was, I felt it was necessary to do it, then I would have done it (used the weapon)...but if I had lived after pressing that button, I could have never forgiven myself.[178] Lord Healey, Secretary of State for Defence and "alternate decision-taker" under Prime Minister Harold Wilson, said that in the event of Soviet nuclear weapons attacking the United Kingdom and the Prime Minister had been killed or incapacitated, he would not have ordered a retaliation.[178]

The process by which a Trident missile-armed submarine would determine if the British government continued to function included, among other checks, establishing whether BBC Radio 4 continued broadcasting.[179]

The special relationship

The 1958 "Agreement For Cooperation on the Uses of Atomic Energy for Mutual Defence Purposes", also known as the "Mutual Defence Agreement", was renewed in 1994 and again in 2005.[180]


The current Trident system cost £12.6 billion (at 1996 prices) and costs £280m a year to maintain. Options for replacing Trident range from £5 billion for the missiles alone to £20–30 billion for missiles, submarines and research facilities. At minimum, for the system to continue after around 2020, the missiles will need to be replaced.[181] The price of replacement of submarine has risen to £31 billion and it is estimated by Ministry of Defence that the cost of trident replacement program for 30 years to be at £167 billion and the Campaign for Nuclear Disarmament puts the cost as high as £205 billion.[182]


After the British government announced its plans to refurbish its Trident SLBM missiles and build new submarines to carry them,[183] it published a white paper The Future of the United Kingdom’s Nuclear Deterrent in which it stated that the renewal is fully compatible with the United Kingdom's treaty commitments and international law.[184] These arguments are summarised in a question and answer briefing published by UK Permanent Representative to the Conference on Disarmament[185]

  • Is Trident replacement legal under the Non Proliferation Treaty (NPT)? Renewal of the Trident system is fully consistent with our international obligations, including those on disarmament. ...
  • Is retaining the deterrent incompatible with NPT Article VI? The NPT does not establish any timetable for nuclear disarmament. Nor does it prohibit maintenance or renewal of existing capabilities. Renewing the current Trident system is fully consistent with the NPT and with all our international legal obligations. ...

At the start of the House of Commons debate to authorise the replacement of Trident,[186] Margaret Beckett stated:

Article VI of the NPT imposes an obligation on all states: "to pursue negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament, and on a Treaty on general and complete disarmament". The NPT Review Conference held in 2000 agreed, by consensus, 13 practical steps towards nuclear disarmament. The UK remains committed to these steps and is making progress on them. We have been disarming. Since the Cold War ended, we have withdrawn and dismantled our tactical maritime and airborne nuclear capabilities. We have terminated our nuclear capable Lance missiles and artillery. We have the smallest nuclear capability of any recognised nuclear weapon state accounting for less than one per cent of the global inventory. And we are the only nuclear weapon state that relies on a single nuclear system.

The subsequent vote was won overwhelmingly, including unanimous support from the opposition Conservative Party.[187]

The Government position remains that it is abiding by the NPT legally in renewing Trident and Britain has the right to possess nuclear weapons, a position reiterated by Tony Blair in PMQs on 21 February 2007.[188]

In contrast, reports by Philippe Sands QC, and by Rabinder Singh QC and Professor Christine Chinkin, used in the case against, were commissioned by the activist groups Greenpeace and Peace Rights respectively.[189] Both groups are opposed to the renewal, use, or proliferation of nuclear weapons.

Furthermore, the British Government and NATO do not recognise advisory opinion of the ICJ,[190] as interpreter of IHL and referred to by Sands et al., (see Advisory Opinion) with regard to use of nuclear weaponry as legally binding.[191]

This position is held in common with all five nuclear states as defined in the NPT.[citation needed] However, only the United Kingdom has expressed its opposition to the establishment of a new legally binding treaty to prevent the threat or use of nuclear weapons against non-nuclear states[192] by its vote in the United Nations General Assembly in 1998.[193]

One view is that the white paper The Future of the United Kingdom’s Nuclear Deterrent stands in contrast to two counsel's opinions. The first, commissioned by Peacerights,[194] was given on 19 December 2005 by Rabinder Singh QC and Professor Christine Chinkin of Matrix Chambers. It addressed '...whether Trident or a likely replacement to Trident breaches customary international law'[195]

Drawing on the International Court of Justice (ICJ) opinion, Singh and Chinkin advised that:

The use of the Trident system would breach customary international law, in particular because it would infringe the "intransgressible" [principles of international customary law] requirement that a distinction must be drawn between combatants and non-combatants.[195]

The second opinion was commissioned by Greenpeace[196] and given by Philippe Sands QC and Helen Law, also of Matrix Chambers, on 13 November 2006.[197] The opinion addressed

The compatibility with international law, in particular the jus ad bellum, international humanitarian law (‘IHL’) and Article VI of the Treaty on the Non-Proliferation of Nuclear Weapons (‘NPT’), of the current UK strategy on the use of Trident...The compatibility with IHL of deploying the current Trident system...[and] the compatibility with IHL and Article VI NPT of the following options for replacing or upgrading Trident: (a) Enhanced targeting capability; (b) Increased yield flexibility; (c) Renewal of the current capability over a longer period.[198]

With regards to the jus ad bellum, Sands and Law advised that

Given the devastating consequences inherent in the use of the UK’s current nuclear weapons, we are of the view that the proportionality test is unlikely to be met except where there is a threat to the very survival of the state. In our view, the ‘vital interests’ of the UK as defined in the Strategic Defence Review are considerably broader than those whose destruction threaten the survival of the state. The use of nuclear weapons to protect such interests is likely to be disproportionate and therefore unlawful under Article 2(4) of the UN Charter.[199]

The phrase "very survival of the state" is a direct quote from paragraph 97 of the ICJ ruling. With regards to international humanitarian law, they advised that

it [is] hard to envisage any scenario in which the use of Trident, as currently constituted, could be consistent with the IHL prohibitions on indiscriminate attacks and unnecessary suffering. Further, such use would be highly likely to result in a violation of the principle of neutrality.[200]

Finally, with reference to the NPT, Sands and Law advised that

A broadening of the deterrence policy to incorporate prevention of nonnuclear attacks so as to justify replacing or upgrading Trident would appear to be inconsistent with Article VI; b) Attempts to justify Trident upgrade or replacement as an insurance against unascertainable future threats would appear to be inconsistent with Article VI; c) Enhancing the targeting capability or yield flexibility of the Trident system is likely to be inconsistent with Article VI; d) Renewal or replacement of Trident at the same capability is likely to be inconsistent with Article VI; and e) In each case such inconsistency could give rise to a material breach of the NPT.[201]


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Further reading

  • Gill, David James. Britain and the Bomb: Nuclear Diplomacy, 1964–1970 (Stanford University Press, 2014) 304pp online review
  • Hicks, George and Roy Dommet, "History of the RAE [Farnborough] and Nuclear Weapons". Prospero, refereed journal of the BROHP, Spring 2005.
  • Rogers, Paul. "Possible Nuclear Attack Scenarios on Britain", Proceedings of the Conference on Nuclear Deterrence, Implications and Policy Options for the 1980s, International Standing Conference on Conflict and Peace Studies, London, 1982.
  • Roy Dommett, "The Blue Streak Weapon". Prospero, refereed journal of the BROHP, Spring 2005.
  • Proceedings of the Royal Aeronautical Society, Symposium on Chevaline 2004, ISBN 1-85768-109-6. See note on sources at Talk:Nuclear weapons and the United Kingdom
  • Dr Peter Jones, Director AWE (Ret), "The Chevaline Technical Programme". Prospero, the refereed journal of the BROHP, Spring 2005.
  • Peter Nailor, The Nassau Connection: the organisation and management of the British POLARIS project, London: H.M.S.O, (1988).
  • Wynn, Humphrey (1997). RAF Strategic Nuclear Deterrent Forces, their origins, roles and deployment, 1946–69. The documentary history. Copyright MoD. Published by The Stationery Office. ISBN 0-11-772833-0.
  • Dr Frank Panton, "The Unveiling of Chevaline". Prospero, the refereed journal of the BROHP, Spring 2005.
  • Dr Frank Panton, "Polaris Improvements and the Chevaline Programme". Prospero, the refereed journal of the BROHP, Spring 2004.

External links