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Weapons of Mass Destruction (WMD)

UK Nuclear Stockpile

Following a fundamental re-examination of the issues, the 1998 Strategic Defence Review concluded that a minimum nuclear deterrent would remain a necessary element of our security. It determined that our deterrence requirements would be met by one Trident332W ballistic missile submarine on patrol at all times carrying 48 nuclear warheads, and a national stockpile of less than 200 operationally available warheads.

During the Second World War, Britain and America cooperated closely in the development of the atomic bomb, with many British scientists involved in the Manhattan Project. Importantly, under the wartime Quebec agreement, Britain surrendered the right to veto American use of atomic weapons. Agreements at the Quebec Conference in 1943, at Hyde Park in September 1944 and in Washington in 1945 promised continuing nuclear cooperation after the end of the war. The McMahon Act of 1946 stipulated that the US would not share information concerning atomic weapons. This was a bitter disappointment to the British government, and as a direct result Attlee's government initiated its own atomic weapons programme in January 1947. This led to the first test at Monte Bello in October 1952.

During the late 1940s and early 1950s the British hoped that pursuing their own atomic weapon programme would force the US to revise the McMahon Act. Instead America used atomic energy information (not atomic weapons information) to bargain for increased access to uranium stocks, obtaining a large quota in the Congo. Negotiations during 1947/8 produced an agreement known as the modus vivendi that allowed exchange of atomic information unrelated to weapons.

Only a limited flow of atomic information arrived in Britain, which was a continual source of disappointment and tension. Cold War tensions mounted after the Korean conflict, which brought an increase in Anglo-American nuclear weapons cooperation. Meetings between Churchill and Dwight D. Eisenhower resulted in the American Atomic Energy Act of 1954, enabling the sharing of information regarding external characteristics of atomic weapons. In the 1950s further agreements were signed between Britain and the US. An agreement in June 1956 provided Britain with information about nuclear submarine propulsion systems that later enabled its nuclear submarine programme. Despite advances in nuclear submarine propulsion, Britain's deterrent was based on RAF jet bombers - the V-bomber force. The British tested their first thermonuclear weapon (the hydrogen bomb) in May 1957. The birth of the nuclear armed ballistic missile made the RAF's V-bomber force out-of-date and expensive.

The fallout from the Suez Crisis forced Britain to reassess defence. The resignation of Anthony Eden as Prime Minister and his replacement by Harold Macmillan allowed for new thinking on strategic policy. Macmillan was keen to develop the concept of Anglo-American nuclear interdependence. In March 1957 Macmillan met Eisenhower in Bermuda and agreed to the deployment of Thor IRBMs in Britain. The British H-bomb test provided a valuable bargaining tool with the Americans and the new Atomic Energy Act of 1958 overturned the McMahon Act. The new act featured an Anglo-American agreement to share information on nuclear weapons, fissile material and the purchase of nuclear materials.

By 1958 Bomber Command had seen a further increase in the hitting power of the V-bomber force, making the effort even more effective as a deterrent. The proportion of Vulcans had steadily increased and deliveries of the Victor had begun. The build-up of the bomber force itself had been accompanied by the build-up of its stockpile of weapons. The growing stock of kiloton weapons was beginning to be supplemented by megaton bombs.

The strategic weapons of V-bomber force and Polaris missile submarines were not the only nuclear weapons deployed by the British. A range of tactical nuclear weapons were also deployed by the Navy, RAF and Army, ranging from nuclear depth charges to attack hostile submarines, free-fall nuclear bombs delivered by jets to short range missiles operated by the Army. However, once the decision to acquire strategic nuclear weapons was made, there was no discussion at Cabinet level about the use or acquisition of 'minor' tactical atomic weapons.

According to the July 1998 Strategic Defense Review [SDR], in current circumstances, nuclear forces continue to make a unique contribution to ensuring stability and preventing crisis escalation. They also help guard against any possible re-emergence of a strategic scale threat to British security. The Review confirmed that in a changing and uncertain world, Britain continues to require a credible and effective minimum nuclear deterrent based on the Trident submarine force. This has provided Britain's only nuclear system since the withdrawal of the last of the RAF's free-fall nuclear bombs earlier this year, performing both the strategic and sub-strategic role. Britain's Trident force provides an operationally independent strategic and sub-strategic nuclear capability in support of NATO's strategy of war prevention and as the ultimate guarantee of British national security.

In May 2010, the government announced that it would reduce the overall size of the UK's nuclear weapons stockpile to 225. A government statement, updated in May 2015, stated: "Following a further review, in October 2010 the Prime Minister announced that by the mid-2020s the overall size of the UK nuclear weapons stockpile will reduce to no more than 180 warheads. No more than 120 will be operationally available."

The program for implementing the reductions in the number of UK nuclear warheads, as announced in the Strategic Defence and Security Review (SDSR), has commenced, Defence Secretary Dr Liam Fox announced 29 June 2011. As part of his statement on the SDSR on 19 October 2010 Prime Minister David Cameron said that the Government had reviewed the UK’s deterrence requirements and concluded that the requirement could be met for an effective and credible deterrent with a smaller nuclear weapons capability.

Cameron said that over the next few years the current deployed capability would be reduced in scale and this reduction would be incorporated into plans for the successor submarine. Therefore the number of warheads on board each submarine would be reduced from a maximum of 48 to a maximum of 40, the number of operational missiles on the Vanguard Class submarines would be reduced to no more than eight, and the number of operational warheads reduced from fewer than 160 to no more than 120.

Dr Fox in a written ministerial statement said:

"I wish to inform the House that the programme for implementing the SDSR warhead reductions has commenced: at least one of the Vanguard Class ballistic missile submarines [SSBN] now carries a maximum of 40 nuclear warheads.

The programme of work to complete these changes across the Vanguard SSBN fleet will be completed within the constraints of the deterrent’s operational programme. We currently expect completion to be made within this Parliament.

The Government does not comment upon the operational programme and therefore ongoing updates on this implementation programme will not be given.

I will update the House further once the changes have been completed across the current SSBN fleet and the SDSR commitment to reducing our stock of operationally deployed warheads has been fulfilled.

On current plans our expectation is that the subsequent reduction in our total stockpile to no more than 180 warheads will complete by the mid-2020s.

The early commencement of the programme for these reductions in warheads is a significant step and further demonstrates the Government’s commitment to fulfilling the UK’s disarmament obligations under the Nuclear Non-Proliferation Treaty.

The Government remains committed to maintaining the minimum credible deterrent necessary to achieve our deterrence objectives of guaranteeing national security."

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Page last modified: 04-02-2018 17:34:12 ZULU