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The Royal Navy officially commissioned HMS Agamemnon, the sixth Astute-class nuclear-powered attack submarine, during a ceremony at BAE Systems’ shipyard in Barrow-in-Furness on 22 September 2025.

King Charles III presided over the event, formally reading the commissioning warrant before attending commemorations in the town, where Barrow was granted Royal Port status.

The event marked a dual milestone for the UK’s naval program. Hours before the Agamemnon ceremony, Defense Secretary John Healey cut the first steel for HMS King George VI, the fourth and final boat of the Dreadnought-class ballistic missile submarines. Together, the developments underscore the continued expansion of Britain’s nuclear-powered submarine fleet, which provides both strike and deterrence capabilities.

Commissioning ceremonies in the UK Royal Navy usually take place after a submarine has completed sea trials and been accepted from the builder. In the case of Agamemnon, the ceremony came before the boat’s first voyage, meaning the vessel will remain at Barrow for approximately 18 months of tests and systems integration before sailing.

Today, HMS Agamemnon formally entered service after a commissioning ceremony with His Majesty The King in Barrow-in-Furness. This marks an important milestone towards another Astute Class submarine joining the @RoyalNavy's fleet.

Read more 👉 https://t.co/yPZzr9qdML pic.twitter.com/brS01mYsCL

— Ministry of Defence 🇬🇧 (@DefenceHQ) September 22, 2025

Agamemnon has already set a record as the longest submarine built in Royal Navy history, with construction stretching over 12 years. Work began with steel cut in July 2013, followed by naming in April 2024, and roll-out from Devonshire Dock Hall in October 2024. Factors behind the lengthy schedule included pandemic disruptions, resource shifts to the Dreadnought program, and design complexity within the wider Astute project.

Astute-Class submarine

The Astute class represents the Royal Navy’s most advanced fleet submarines, designed to replace the ageing Trafalgar class. Each boat incorporates a mix of stealth, endurance, and firepower to support a wide range of operations, from strategic deterrence protection to precision land attack.

• Size and structure: HMS Agamemnon measures 97 meters in length, with a displacement of around 7,400 tons.
• Power and endurance: Propelled by a Rolls-Royce PWR2 pressurised water reactor with pump-jet propulsion, the boat has effectively unlimited range, limited only by food supplies and crew endurance, typically about 90 days. The reactor is designed to last the lifetime of the submarine without refueling.
• Performance: The submarine can dive beyond 300 meters and reach submerged speeds of up to 30 knots (56 kilometers per hour).
• Crew: Standard complement is about 98 personnel, with capacity for up to 109.
• Sensors: Combat systems integrate the Thales Sonar 2076 suite and CM010 optronic masts, providing advanced detection, tracking, and targeting capabilities.
• Weapons: Six 533-millimeter torpedo tubes allow storage of up to 38 weapons. The submarine is armed with Spearfish heavyweight torpedoes and Tomahawk cruise missiles. Tomahawk Block V, expected to replace earlier versions, offers a range of approximately 1,000 miles with enhanced targeting and in-flight communication.

Missions for Astute-class submarines include escorting the UK’s continuous at-sea deterrent, supporting carrier strike groups, securing undersea infrastructure, gathering intelligence, and deploying special forces.

Dreadnought-Class Submarine

Alongside the commissioning, the Royal Navy launched the next stage of its strategic deterrent program. The first steel was cut for HMS King George VI, the last of four Dreadnought-class submarines intended to replace the Vanguard class in the early 2030s.

The Dreadnought class will be the largest submarines ever constructed for the Royal Navy:

• Size: 154 meters in length, displacing around 17,200 tonnes.
• Crew: Designed to carry up to 130 personnel.
• Power: Equipped with the Rolls-Royce PWR3 reactor, geared steam turbines, and a single propeller shaft.
• Performance: Capable of speeds up to 20 knots on the surface and 28 knots submerged.
• Armament: The boats will carry Spearfish torpedoes and Trident II ballistic missiles, forming the backbone of the UK’s nuclear deterrent mission known as Operation Relentless.

Strategic Importance

The Barrow-in-Furness shipyard, managed by BAE Systems, remains at the center of UK submarine construction. More than 13,500 jobs are linked to defense nuclear programs in the town, with projections for further growth as Astute production winds down and Dreadnought builds accelerate.

Steve Timms, managing director of BAE Systems’ Submarines business, said the commissioning and steel-cutting ceremonies reflected both tradition and progress, “Cutting steel on the fourth Dreadnought submarine demonstrates the significant progress we’ve made on the program, whilst the sixth Astute-class boat, HMS Agamemnon, joins the long and distinguished list of Barrow-built vessels to be commissioned into the Royal Navy.”

“The enduring partnership between our Barrow shipyard and the Navy dates back to the Victorian age, and our role as the UK’s home of submarine design and build is something we’re incredibly proud of,” he added.

HMS Agamemnon is the penultimate Astute-class boat, with the final submarine, renamed HMS Achilles, expected to enter service by 2028 or 2029. The Astute fleet will eventually give way to a new generation of attack submarines developed under the SSN-AUKUS program, designed to replace the Astute class from the late 2030s onward.

Under current plans, the Royal Navy will rotate an attack submarine to HMAS Stirling in Western Australia from 2027, deepening integration with allies under the AUKUS partnership.