The Defence Investment Plan identifies the initiative as the “Dreadnought successor” but does not specify its platform, configuration, cost or timetable. At this stage, the government has committed to defining the requirement rather than launching a formal acquisition programme.
Four Dreadnought-class ballistic-missile submarines are being built at Barrow-in-Furness and are set to enter service from the early 2030s. They will deliver Britain’s next-generation strategic deterrent and sustain its Continuous At Sea Deterrent.
Their construction forms part of the government’s nuclear “triple lock”, which also commits Britain to maintaining continuous deterrent patrols and delivering future upgrades. The existing Vanguard-class submarines will continue to receive support at Clyde and Devonport during the transition.
The sequencing means Britain will maintain the Vanguard fleet, introduce Dreadnought and begin preparing for the system that follows it at the same time. It establishes a long-term policy direction even though the central technical and procurement choices remain open.
The Ministry of Defence has allocated £63.6 billion to the Defence Nuclear Enterprise between the 2026-27 and 2029-30 financial years, excluding workforce costs. Submarines account for £47 billion of that allocation, including expenditure on maintenance and infrastructure.
Spending on the nuclear enterprise is expected to represent about 20% to 25% of the ministry’s overall budget. The government plans to invest more than £20 billion above the amount spent during the previous four-year period to modernise and sustain the deterrent.
A further £6 billion is being directed towards expanding and transforming submarine manufacturing capacity between 2025-26 and 2029-30. The nuclear supply chain includes more than 6,000 UK-based companies, while employment across the sector is expected to reach 65,000 by 2030.
The industrial programme is supported by a multi-decade, multi-billion-pound investment at HM Naval Base Clyde, including preparations for Dreadnought. Britain is also acquiring three floating docks at Faslane to provide out-of-water engineering support across its submarine fleet.
Devonport is receiving infrastructure investment for submarine maintenance, recycling and long-term fleet support. The plan also provides £1.7 billion to explore re-establishing a defence reactor fuel cycle and £290 million for nuclear skills.
The wider investment includes the £9 billion Unity contract awarded to Rolls-Royce in January 2025 for reactor design, production and support. An expanded Submarine Production Alliance brings together the Ministry of Defence, BAE Systems, Rolls-Royce and Babcock to improve delivery of Dreadnought and SSN-AUKUS submarines.
The plan places Britain’s future deterrent work within its established nuclear relationships with the United States and France. Cooperation with Washington continues under the 1958 Mutual Defence Agreement and the 1963 Polaris Sales Agreement, although the document does not identify a US role in the post-Dreadnought programme.
No design competition, industrial structure or delivery schedule has yet been announced for the future deterrent. The decision nevertheless shows that Britain is managing its nuclear capability across three generations: sustaining Vanguard, delivering Dreadnought and defining what will follow.
