British Navy commissions sixth Astute-class nuclear submarine HMS Agamemnon.

HMS Agamemnon, the sixth Astute-class submarine, was formally commissioned in Barrow-in-Furness on Sept. 22, 2025, during a ceremony led by King Charles III.

On September 22, 2025, the sixth Astute-class nuclear submarine HMS Agamemnon was formally commissioned at BAE Systems’ shipyard in Barrow-in-Furness during a ceremony attended by approximately 500 people. His Majesty King Charles III presided over the event, reading the commissioning warrant before visiting Barrow Town Hall, where Royal Port status was granted to the town. On the same day, the first steel was cut for HMS King George VI, the fourth Dreadnought-class submarine, underlining the parallel development of two major submarine programs at Barrow.
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HMS Agamemnon is the sixth nuclear attack submarine of the seven-unit Astute class and the penultimate attack submarine of this series for the Royal Navy. (Picture source: British Navy)

Steel for the HMS Agamemnon was cut in July 2013, and the submarine was officially named in April 2024. Roll-out from the Devonshire Dock Hall occurred on October 2, 2024, followed by the launch the next day. Commissioning in September 2025 concluded more than twelve years of build work. Reports noted that delays were influenced by factors such as pandemic disruptions, resource allocation to the Dreadnought program, and the complexity of the Astute design. Commissioning is only one step before operational readiness, as the HMS Agamemnon will remain in Barrow for final test and commissioning work, which includes basin trials and systems integration, before beginning sea trials and eventually transferring to HM Naval Base Clyde. The name Agamemnon continues a Royal Navy tradition dating back to the eighteenth century, and the boat carries a battle honours board crafted from oak timbers of a previous vessel with the same name, linking it to earlier service history.

HMS Agamemnon is the sixth submarine of the Astute class, a series of seven nuclear-powered attack submarines, and is the penultimate unit of the program. The submarine measures about 97 meters in length, displaces roughly 7,400 tonnes, and is powered by a Rolls-Royce PWR2 pressurised-water reactor with pump-jet propulsion. The reactor is designed to last for the life of the boat without requiring refuelling, with operational endurance determined by supplies and crew limitations, generally around 90 days. The combat system integrates the Thales Sonar 2076 suite, CM010 optronic masts, and other sensors. Armament is carried in six 533 mm torpedo tubes with storage for up to 38 weapons, typically Spearfish heavyweight torpedoes and Tomahawk land-attack cruise missiles, which give the submarine a strike range of about 1,000 miles. The Royal Navy has stated that Tomahawk Block V will be introduced to replace earlier versions, providing enhanced in-flight communication and targeting. Crew complement is approximately 98, with the option to accommodate additional personnel.

Within the current Royal Navy structure, Astute-class submarines such as Agamemnon have missions that include escorting the Continuous at Sea Deterrent, supporting carrier strike groups, securing undersea infrastructure, gathering intelligence, and deploying special operations forces from a submerged platform. Their torpedoes and cruise missiles allow both sea-denial and land-attack roles, while the sensor systems provide detection and tracking across the undersea environment. Agamemnon is joining a fleet in which submarine availability has been affected by extended maintenance and refit schedules. Earlier in 2025, HMS Prince of Wales operated in the Pacific without a submarine escort because HMS Anson returned to Clyde, while HMS Ambush and HMS Artful were reported inactive for prolonged periods. The introduction of Agamemnon is expected to help improve availability by increasing flexibility as boats rotate through upgrades and dockings. Once trials are complete, Agamemnon will join five Astute-class submarines at HM Naval Base Clyde.

The Astute class as a whole represents the current generation of UK nuclear-powered attack submarines, replacing the Trafalgar class. Each boat incorporates the PWR2 reactor, pump-jet propulsion, integrated sonar arrays, and the use of optronic masts instead of traditional periscopes. The program totals seven boats, with six now commissioned and the final unit still under construction. The last submarine was originally to be named Agincourt but has since been renamed HMS Achilles, with entry into service projected between 2028 and early 2029. Open sources cite National Audit Office forecasts that placed the cost of Boat 6, Agamemnon, at about £1.533 billion, situating it mid-range within the class in terms of expenditure. The program experienced early difficulties in design and construction that required external expertise, particularly in 3D computer-aided design and vertical outfitting, but subsequently stabilized into a steady build rhythm. Agamemnon’s arrival, therefore, comes near the close of the Astute build cycle while preparations for future submarines intensify.

The commissioning event was used to emphasize the continuity of UK submarine programs at Barrow, particularly the parallel progression of Astute and Dreadnought work. The first steel cut for HMS King George VI began fabrication of the fourth Dreadnought-class submarine, which will replace the Vanguard class in the early 2030s and maintain the UK’s nuclear deterrent under Operation Relentless. Royal Port status for Barrow formally recognized more than a century of submarine construction at the town, acknowledging its central role in sustaining the defence nuclear sector. Official statements highlighted workforce expansion, investment in new facilities, and the training of apprentices and graduates to maintain output. Figures cited for 2024 indicated over 13,500 jobs in Barrow linked to the defence nuclear sector, with projections of further growth as Astute construction concludes and Dreadnought builds accelerate. This industrial framework ensures continuity of skills and infrastructure as the UK moves from one submarine generation to the next.

Looking toward the future, HMS Agamemnon occupies a transitional position between the Astute class and its planned replacement. Policy statements tied to the Strategic Defence Review refer to increasing the number of fleet submarines during the 2030s, while the trilateral SSN-AUKUS program is intended to deliver a new attack submarine design to replace the Astute class from the late 2030s onward. Under current planning, the Royal Navy will rotate a nuclear-powered attack submarine to HMAS Stirling in Western Australia beginning in 2027, integrating with allied presence and training in the Indo-Pacific. In the near term, Agamemnon strengthens the attack submarine force, providing additional availability for deterrent protection, carrier strike group support, undersea infrastructure security, and allied operations. In the long term, the commissioning marks one of the final steps in the Astute program before the transition to SSN-AUKUS, connecting current capability to the strategic fleet structure planned for the next decade.

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.