Nuclear weapons profile: United Kingdom
This paper briefly examines the UK's nuclear weapons policies, capabilities and programmes. It is one paper in a larger series on the nuclear weapon states.
The UK has been a nuclear weapon state since 1952. It is one of the five officially recognised nuclear states under the Nuclear Non-Proliferation Treaty (NPT).
Nuclear postureThe UK adopts a posture of minimal credible nuclear deterrence, assigned to the defence of NATO. The UK does not have a policy of ‘no-first use’.
Between the end of the Cold War and 2021, the UK took several disarmament steps in support of the NPT. It withdrew all other nuclear weapons systems except for its submarine-launched Trident system and made changes to the operational status of the deterrent.
Under commitments outlined in the 2010 Strategic Defence and Security Review (SDSR), the UK was expected to have achieved, by the mid-2020s, a 65% reduction in the size of its overall nuclear stockpile since the height of the Cold War.
The 2021 Integrated Review announced, however, that the 2010 commitments could no longer be met due to the current security environment. As such, it announced that the cap on the nuclear stockpile would be raised and that information on the UK’s operational stockpile, deployed missiles and deployed warheads would no longer be made available. Both decisions led many to question the UK’s commitment to disarmament.
In June 2025, the government announced that the UK would also join the NATO nuclear deterrence mission by purchasing 12 F-35A dual-capable aircraft that could deploy with US nuclear weapons in times of crisis.
Headlines:
- Nuclear stockpile – Prior to the 2021 Integrated Review, the UK had a stockpile of 225 warheads. Following the review, the cap on the UK’s nuclear stockpile will increase to no more than 260 warheads. The Government has provided no timeframe for achieving this increase and no longer publishes transparency information, so the precise figure for the stockpile is unclear.
- The UK is the only nuclear weapon state that has reduced to a single deterrent system. The decision to join the NATO nuclear mission is intended to “complement” the UK’s independent submarine-based strategic nuclear deterrent and does not involve the procurement of a sovereign air-launched capability.
- Operates continuous at-sea deterrence (CASD) through Operation Relentless.
The programme to replace the UK’s nuclear deterrent has been underway since 2006. It involves the replacement of the Vanguard class submarines (SSBN) with a new Dreadnought class of SSBN from the early 2030s. The estimated cost of the design and manufacture of a class of four SSBN is £31 billion, including inflation over the life of the programme. A £10 billion contingency has also been set aside.
The UK is participating in the current US service-life extension programme for the Trident II D5 missile, and in February 2020 the Government confirmed that a programme to replace the UK’s Mk4 nuclear warhead is also underway. The 2025 Strategic Defence Review confirmed £15 billion in funding for the replacement warhead programme, in this Parliament (to 2029).
This short paper is intended as an introduction to the UK’s nuclear weapons policies and programmes. It is part of a series of country profiles which are available on the House of Commons Library website.