The Royal Navy is responsible for providing the UK’s strategic nuclear deterrent. Since April 1969 the Royal Navy has always had one ballistic missile submarine on patrol at any one time on operation Relentless. This is known as continuous-at-sea deterrent (CASD) and was originally provided by the submarine-based Polaris system, in which Resolution-class submarines carried Polaris ballistic missiles. The Royal Navy formally assumed responsibility for the UK’s strategic nuclear deterrent in June 1969 from the RAF’s V-force. The deterrent has been solely submarine-based since the withdrawal of the RAF’s WE-177 free-fall bombs in the late 1990s.

CASD is now provided by the four Vanguard-class submarines carrying the Trident missile system. In a vote in July 2016 the House of Commons approved the decision to maintain the UK’s nuclear deterrent beyond the early 2030s. The Vanguard-class submarines will be replaced by the new Dreadnought-class. The first is expected to enter service in the early 2030s and have a service life of at least 30 years. Three of the four Dreadnought submarines have been named – Dreadnought, Valiant and Warspite.

The cost of the design and manufacture of a class of four submarines has been estimated at £31 billion, including defence inflation over the life of the programme. A £10 billion contingency has also been set aside. Once the new nuclear deterrent comes into service the annual in-service costs are expected to continue at approximately 6% of the defence budget.

The UK is separately participating in the US’ current service-life extension programme for the Trident II D5 missile, which will extend the life of the Trident missile potentially to the early 2060s. Decisions on a replacement warhead have also been deferred until later in this Parliament.

Library papers for further reading

Replacing the UK’s nuclear deterrent: progress of the Dreadnought class

The cost of the UK’s strategic nuclear deterrent

Replacing the UK’s ‘Trident’ nuclear deterrent

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