UK begins construction of final Dreadnought-class nuclear submarine HMS King George VI.

The UK has begun building HMS King George VI, its fourth and final Dreadnought-class nuclear ballistic missile submarine, at BAE Systems’ Barrow-in-Furness shipyard. The program secures Britain’s nuclear deterrent into the 2030s as the Vanguard-class fleet retires.

On September 22, 2025, the United Kingdom formally began the construction of the HMS King George VI, the fourth and final Dreadnought-class ballistic missile submarine, with a steel-cutting ceremony at BAE Systems’ Barrow-in-Furness facility on the same day. Defence Secretary John Healey presided over the event, which marked the start of work on a submarine scheduled to enter service in the early 2030s.
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The Dreadnought-class comprises the HMS Dreadnought, the HMS Valiant, the HMS Warspite, and the HMS King George VI, which are scheduled to take over the nuclear deterrent role as Vanguard-class units retire in the 2040s. (Picture source: British Navy)

This milestone coincided with the commissioning of HMS Agamemnon, an Astute-class nuclear attack submarine, and the conferral of Royal Port status on Barrow by King Charles III, an acknowledgement of the town’s centrality to submarine construction in the United Kingdom. The Dreadnought programme is intended to maintain the country’s continuous at-sea deterrent posture, a policy in place since 1969, and HMS King George VI represents the final unit in a four-boat fleet designed to ensure uninterrupted deterrent patrols.

The Dreadnought class is being constructed to replace the Vanguard-class, which has provided the UK’s nuclear deterrent since the 1990s. The four vessels, HMS Dreadnought, HMS Valiant, HMS Warspite, and HMS King George VI, are intended to maintain the ability to deploy one submarine on patrol at all times while others are in port for maintenance or training. Each submarine has a planned service life of between 35 and 40 years, compared to 25 years for Vanguard, and will have a crew complement of around 130. Dimensions include a length of 153.6 metres and a displacement of approximately 17,200 tonnes. These features make the Dreadnought class larger than its predecessors, providing additional internal space for equipment, crew accommodations, and safety improvements.

Propulsion is based on Rolls-Royce’s PWR3 nuclear reactor, coupled with a turbo-electric drive and pump-jet propulsion system. The PWR3 reactor was chosen over earlier PWR2 designs for its improved safety performance, longer lifespan, reduced maintenance requirements, and simplified operations. The submarines also incorporate X-rudders for enhanced manoeuvrability and acoustic discretion, a first for British boats, and employ a fly-by-wire Active Vehicle Control Management system to improve handling. Each Dreadnought will carry 12 Trident II D5 ballistic missile tubes arranged in a common missile compartment design developed in partnership with the United States for both the Dreadnought and Columbia classes. Four 533 mm torpedo tubes will carry Spearfish heavyweight torpedoes, providing a conventional self-defence and anti-submarine capability in addition to the strategic missile load.

Industrial and supply-chain activity supporting the programme spans multiple sites across the United Kingdom. Thales Glasgow holds a £193 million contract to deliver optronic masts, while General Dynamics Mission Systems is responsible for the fire-control systems that are common to both the Dreadnought and Columbia classes. Babcock has been contracted to manufacture 75 missile-tube assemblies at its Rosyth and Bristol facilities, and Northrop Grumman supplies launcher subsystem hardware under a $458 million contract. Rolls-Royce is contracted under the £9 billion “Unity” agreement announced in January 2025 to oversee research, design, manufacture, and support for all nuclear submarine reactors over an eight-year period, covering Dreadnought and Astute propulsion systems. Barrow continues to host the main construction facilities, and some specialist steels have been sourced outside the UK, reflecting globalised supply patterns despite efforts to secure domestic production capability.

Programme milestones reflect a phased schedule to maintain deterrence continuity and industrial capacity. Steel for HMS Dreadnought was cut in October 2016, and the vessel was formally laid down on 20 March 2025 after completion of its pressure hull in December 2022. Missile tubes for the class arrived from the United States in December 2022, and work on HMS Valiant began in 2019, followed by HMS Warspite in February 2023. With steel cut for HMS King George VI in September 2025, all four boats are under construction. The Ministry of Defence states the programme remains on track for an early 2030s entry into service for HMS Dreadnought, with Vanguard-class retirement phased through the 2040s to ensure uninterrupted deterrent coverage. Coordination with the United States on the common missile compartment ensures synchronisation of timelines and maintains compatibility across both navies’ strategic submarine fleets.

Cost projections for the Dreadnought programme have evolved since the early planning stages. The Initial Gate report in 2011 estimated costs at £25 billion, revised to £31 billion in 2015 with a £10 billion contingency reserve. Adjusted for inflation, this equates to £38.85 billion in 2023, or around £9.71 billion per submarine. The Ministry of Defence accessed £2 billion of the contingency fund in 2023 to bring forward spending. Lifetime costs, including infrastructure, missile renewal, support, and decommissioning, have been estimated between £172 billion and £205 billion, while a parliamentary estimate cited £179 billion. Annual in-service costs are projected at about £3 billion, roughly 6% of the defence budget. As of 31 March 2024, £17.4 billion had been spent on early phases and £3.37 billion of contingency had been used, with the rest scheduled for later years. The National Audit Office has flagged affordability risks across the wider defence programme, though the Ministry of Defence has stated the Dreadnought class remains within forecast costs.

Employment and skills remain core elements of the programme alongside the deterrent capability. The Ministry of Defence reports that the UK’s defence nuclear sector employs over 47,000 people nationwide, with forecasts of 65,000 jobs by 2030 as construction and related infrastructure projects progress. At Barrow, more than 13,500 people are employed in submarine programmes, including approximately 1,800 apprentices and 500 graduates in training at BAE’s Submarines Academy for Skills and Knowledge. The granting of Royal Port status to Barrow reflects this industrial concentration and the town’s importance to long-term submarine construction. Across the supply chain, BAE Systems has identified 1,500 domestic companies contributing to the project, representing £7.5 billion of work distributed across the UK. These efforts are aligned with the Defence Nuclear Enterprise strategy, which is intended to ensure the long-term sustainment of Britain’s nuclear deterrent through industrial, financial, and operational planning.

Written by Jérôme Brahy

Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.