Select Committee on Defence Ninth Report

2  The UK's nuclear deterrent

Table 1: The components of the UK's current nuclear deterrent

Platform	4 Vanguard-class nuclear-powered ballistic missile submarines, built in the UK
Missile	Each submarine is capable of carrying up to 16 Trident D5 submarine-launched intercontinental ballistic missiles, sourced from the US
Warhead	Each missile is capable of carrying 12 nuclear warheads, manufactured in the UK, but since 1998 the number of warheads per missile was has been limited to 3 warheads, and 48 warheads in total per submarine
Shore Infrastructure	The Vanguard submarines are based at HM Naval Base Clyde at Faslane Nuclear warheads are fitted to the missiles at the Royal Naval Armaments Depot Coulport (part of HM Naval Base Clyde)
Warhead production and maintenance	The nuclear warheads are manufactured by the Atomic Weapons Establishment at Aldermaston and Burghfield, in Berkshire
Industrial base	The Vanguard submarines were designed and built by BAE Systems Submarines at Barrow-in-Furness, in Cumbria Refit and maintenance is carried out by Devonport Management Limited at Devonport in Plymouth The submarines' Nuclear Steam Raising Plants, including the nuclear reactors, are built by Rolls-Royce at Raynesway in Derbyshire There is an extensive supply chain

Components of the UK's nuclear deterrent

8. The UK's strategic nuclear deterrent is based upon the Trident weapons system. It is the UK's third-generation nuclear deterrent. It was developed during the final decade of the Cold War, and was introduced into service over a six-year period beginning in December 1994. It is the UK's sole nuclear weapons system: the UK disposed of its land-based Lance system, and air-launched WE 177 free-fall nuclear bombs in the 1990s.

9. The deterrent has three technical components:

• the Vanguard-class nuclear-powered ballistic missile submarine (SSBN), of which the UK has four, HMS Vanguard, Victorious, Vigilant and Vengeance, designed and built in the UK by Vickers Shipbuilding and Engineering Ltd. (VSEL), now BAE Systems, in Barrow-in-Furness, Cumbria.
• the Trident D5 submarine-launched intercontinental ballistic missile, manufactured in the USA by Lockheed Martin. Under the Polaris Sales Agreement (modified for Trident), the UK has title to 58 missiles, of which it has now used 8 in tests. Aside from those currently deployed, the missiles are held in a communal pool at the US Strategic Weapons facility at King's Bay, Georgia, USA.
• the nuclear warhead, designed and manufactured in the UK at the Atomic Weapons Establishment, Aldermaston and Burghfield in Berkshire. Each missile is capable of carrying 12 warheads, but since the 1998 Strategic Defence Review, the number of warheads per missile has been limited to 3 warheads (and 48 warheads in total per submarine).

10. The submarine fleet is supported by an extensive onshore infrastructure. This is described in detail in our second report.[6]

Operating posture of the UK's nuclear deterrent

11. The 1998 Strategic Defence Review (SDR) stated that the UK would continue to maintain continuous-at-sea deterrent (CASD) patrols. This meant that one of the UK's four Vanguard-class submarines would be on patrol at any give time. The SDR stated that the purpose of CASD was "to avoid misunderstanding or escalation if a Trident submarine were to sail during a period of crisis".[7] By keeping one submarine on patrol at all times, the UK avoids the risk of sending incorrect or misleading signals to a potential adversary at times of heightened alert. In our first report on the future of the UK's strategic nuclear deterrent, we suggested that if the MoD believed the UK should retain the continuous-at-sea deterrent cycle, it must either extend the life of the Vanguard-class submarine or procure a new platform to be in service by around 2020. The issue of maintaining continuous-at-sea deterrence is at the heart of the debate over the timing of decisions on the future of the UK's nuclear deterrent.

12. According to the MoD, a four boat fleet is normally required to guarantee one boat on patrol at all times, because one boat is either preparing to enter refit, in refit, or leaving refit and preparing to re-enter service, one is in maintenance between patrols, and one is either on its way to take up patrol or returning from patrol. By the time Vanguard goes out-of-service the last refit will have been completed, and so it will only be when Victorious goes out-of-service in 2024 that the MoD says the continuous-at-sea regime could not be sustained.

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6   HC (2006-07) 59, paras 12-21 Back

7   Cm 3999, p 19 Back

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Prepared 7 March 2007