UK submarine fleet

The Royal Navy currently has a fleet of nine submarines, with two Astute class attack submarines still to enter service by the end of 2026. A programme to replace the ballistic missile submarines of the nuclear deterrent fleet is currently underway, while the UK is also working with the United States and Australia on a next generation conventional attack submarine that will eventually replace the Astute. There are longstanding concerns over maintenance and availability of the submarine fleet, along with manpower and skills shortages in the submarine service. A pilot project that will inform a longer-term programme to dismantle the Royal Navy’s decommissioned nuclear submarines began in 2023.  

Size of the fleet

The Royal Navy currently operates a fleet of nine submarines. Five of those are conventionally-armed nuclear-powered attack submarines of the Astute class. A further four are ballistic missiles submarines (SSBN) of the Vanguard class that comprise the UK’s submarine-based nuclear deterrent.

The Royal Navy’s final attack submarine of the Trafalgar class, HMS Triumph, retired from service in December 2024 and will be officially decommissioned in early 2025.

A further two Astute class submarines, HMS Agamemnon and HMS Agincourt, are yet to enter service. HMS Agamemnon was launched in October 2024 and is currently undergoing a test and commissioning programme before undertaking sea trials with the Royal Navy. The boat is expected to enter service later in 2025. HMS Agincourt remains under construction and is expected to enter service as the last of the seven boat Astute class in late 2026.

Basing of the fleet

The Royal Navy’s entire submarine fleet is based at HMNB Clyde (Faslane) after a decision was taken in May 2009 to designate Faslane as their home port and to develop a submarine centre of excellence there by 2020. Since 2015, HMNB Clyde has received over £1.8 billion in infrastructure funding to accommodate the submarine fleet, and to prepare for the entry into service of the Dreadnought class SSBN in the early 2030s. HMNB Clyde is one of Scotland’s largest employers, employing over 6,000 military and civilian personnel.

While routine maintenance of submarines takes place at HMNB Clyde, major refit, maintenance and the decommissioning of all Royal Navy nuclear-powered submarines takes place at HMNB Devonport in Plymouth.

Concerns over the fleet

There are longstanding concerns over manpower and skills shortages in the submarine service. Questions have also been asked, most recently by the Defence Select Committee (PDF) over the impact that extended periods of maintenance have had on the  availability of the Royal Navy’s attack submarines and whether the fleet will be able to sustain both its current tasks and the additional deployments to Australia that are envisaged from 2026 under the AUKUS agreement (see below).

Replacement of the Vanguard class SSBN

Following a decision in the House of Commons in July 2016 to maintain the UK’s nuclear deterrent beyond the early 2030s, work is currently underway on the Dreadnought SSBN programme. That project will see the construction of four new Dreadnought class SSBN to replace the current Vanguard class from the early 2030s onwards.

Construction of the first three boats of the class, HMS Dreadnought, HMS Warspite and HMS Valiant, is underway. Work on the fourth boat, HMS King George VI is yet to start.

BAE Systems and Rolls Royce are the main industrial partners (prime contractors) in this project, which the MOD estimates is supporting 42,000 jobs and 2,500 suppliers across the UK, either directly or indirectly.

The cost of the Dreadnought programme has been estimated at £31 billion, including inflation over the life of the programme. A £10 billion contingency has also been set aside, giving a potential programme total of £41 billion.

The Defence Nuclear Enterprise

In 2023 changes were made to the funding arrangements for the nuclear deterrent. All nuclear programmes and expenditure across the Ministry of defence (including all of the Royal Navy’s nuclear-powered submarines), including annual in-service costs, have now been brought under one heading: the Defence Nuclear Enterprise (DNE). That spending has also been ringfenced within the departmental budget, reflecting the increasing interdependence between the nuclear deterrent and the Royal Navy’s other conventional nuclear-powered submarine programmes, including the new AUKUS-SSN. This is particularly relevant to costs associated with basing, infrastructure and nuclear propulsion. DNE spend now appears as a single line in the departmental estimates.

The UK’s next generation attack submarine (AUKUS- SSN)

Design work on the UK’s next generation submarine was underway as part of the Submersible Ship Nuclear Replacement (SSN-R) programme and in 2021 BAE Systems and Rolls Royce were both awarded £85 million contracts to consider the design and capabilities of any successor to the current Astute class attack submarine.

In September 2021, however, Australia, the UK and the United States announced a new defence and security partnership, referred to as AUKUS. A major part of the agreement is to support Australia in acquiring its first conventionally armed, nuclear-powered submarine (SSN) fleet (referred to as pillar 1 of AUKUS).

SSN-AUKUS will be based on the UK’s next-generation submarine design, developed under the SSN-R programme, and will incorporate technologies from all three AUKUS nations, including cutting edge US submarine technologies.

The submarines will be built in the UK and Australia and work will begin by 2030, with a view to entering service toward the end of the 2030s (UK) and the early 2040s (Australia). At its peak, over 21,000 people will be working on the AUKUS-SSN programme in the UK (PDF), including an additional 1,700 jobs at Rolls Royce in Derby.

The UK and Australia will both operate the SSN-AUKUS as their conventionally armed attack submarine, equipped for intelligence, surveillance, undersea warfare and strike missions.

Submarine Dismantling Project

Since 1983 decommissioned Royal Navy submarines have been defueled and stored afloat at either Rosyth or Devonport dockyards, awaiting dismantlement. Seven Royal Navy submarines remain stored afloat at Rosyth. A further 15 are currently at Devonport, although not all submarines have been defueled. The decommissioning of HMS Triumph will also take place at Devonport in early 2025.

The MOD’s Submarine Dismantling Project (SDP) is currently underway to develop a dismantling and disposal solution for the Royal Navy’s existing decommissioned submarines and the four submarines of the Vanguard class SSBN which will leave service from the early 2030s onwards. The Submarine Dismantling Project is based at Rosyth Dockyard. In 2023, HMS Swiftsure, which is being used as a pilot for the SDP was dry-docked to begin the final stages of dismantling. Swiftsure is expected to be fully dismantled by the end of 2026 with 90% of components expected to be reused or recycled.

That project will act as a blueprint for dismantling the Navy’s remaining decommissioned nuclear submarines. A contract for the next two submarines to be dismantled is expected to be placed in 2025.