Nuclear weapons at a glance: United Kingdom

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 policy 

The 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’.

Position on disarmament 

Since the end of the Cold War, the UK has taken a number of disarmament steps in support of the NPT. It has withdrawn all other nuclear weapons systems except for its submarine-launched Trident system. It has made changes to the operational status of the deterrent and been increasingly transparent about its nuclear inventory.

Under commitments outlined in the 2010 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.

However, the 2021 Integrated Review announced 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 will now be raised and that information on operational stockpile, deployed missiles and deployed warheads would no longer be made available. Both decisions have led many to question the Government’s commitment to disarmament.

Nuclear capabilities 

• Nuclear stockpile – A ceiling of no more than 260 warheads. The precise figure for the stockpile is unclear.
• The UK is the only nuclear weapon state that has reduced to a single deterrent system.
• Operates continuous at-sea deterrence (CASD).

Modernisation – the Dreadnought and replacement warhead programmes

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 also participating in the current US service-life extension programme for the Trident II D5 missile.

In February 2020 the Government confirmed that a programme to replace the UK’s Mk4 nuclear warhead was also underway.

In March 2024, the Conservative government published a new Defence Nuclear Command Paper which set out the long-term approach to investing in, and maintaining, the nuclear deterrent as part of a broader strategy to support the UK’s defence nuclear industry.

Commitment to the nuclear deterrent by the new Labour government 

In July 2024 the new Labour government reaffirmed its commitment to the nuclear deterrent. It also launched a Strategic Defence Review, which will examine, among other things “the efficiency and effectiveness of the nuclear programme”. The SDR is due to report in the first half of 2025.

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.