The UK will begin defining the requirement for the submarines that will one day replace the Dreadnought class, with the Defence Investment Plan committing to start work on the post-Dreadnought strategic deterrent within this Parliament.
The plan lists among its nuclear investments “starting to define the requirement for the post-Dreadnought strategic deterrent within this Parliament,” a commitment made while the four Dreadnought boats themselves remain under construction at Barrow-in-Furness, with the class not due to enter service until the early 2030s. Steel was cut on the fourth and final boat, HMS King George VI, last year, joining Dreadnought, Valiant and Warspite in build.
Beginning successor work this early reflects one of the hardest-learned lessons of the British submarine enterprise. The gap in orders that followed the Vanguard class contributed to the loss of skills and industrial capacity that the programmes of the past two decades have spent heavily to rebuild, and the Ministry of Defence signalled its intent to avoid repeating the cycle when it began early concept studies on post-Dreadnought submarines last year, work aligned with allied strategic planning.
The Dreadnought boats are designed for a service life of decades, meaning their replacements would not be needed until well past mid-century, but the design, industrial and warhead decisions that shape a deterrent platform run on timescales measured in decades rather than years.
The commitment is within a wider nuclear package in the plan. The Vanguard class will be maintained at Clyde and Devonport while it continues to carry the deterrent, and the warhead programme will sustain the current Mk4A while designing its replacement, Astraea, supported by £15 billion announced in the Strategic Defence Review for the warhead programme between 2025-26 and 2029-30. That includes strategic investment at AWE Aldermaston, Burghfield and RNAD Coulport, completion of the MENSA warhead assembly and disassembly facility, and construction of a Future Materials Campus to transform nuclear material manufacturing, storage and recovery. A £1.7 billion Nuclear Fuels Programme will explore re-establishing a defence nuclear fuel cycle, and £6 billion goes to expanding and transforming submarine manufacturing between 2025-26 and 2029-30.
The plan also describes the deterrent within the UK’s alliances, citing the 1958 Mutual Defense Agreement and 1963 Polaris Sales Agreement with the United States and a strengthening relationship with France on nuclear policy, capabilities and operations under the 2025 Northwood Declaration. Total deterrent spending across Dreadnought, SSN-AUKUS and the warhead runs to £63 billion over the next four years.
The plan gives no detail on what form the post-Dreadnought platform might take, its numbers, or when a design decision would be expected, with the commitment limited to beginning the requirement definition before the current Parliament ends.
Best plan for a different missile.