Royal Navy’s HMS Agamemnon Astute-Class Nuclear Powered Attack Submarine Successfully Completes Trim Dive

The Royal Navy's sixth Astute-class nuclear-powered attack submarine, HMS Agamemnon (S123), has successfully completed a three-day trim dive at Devonshire Dock in Barrow-in-Furness. This milestone is critical to testing the submarine’s stability, internal weight distribution, watertight integrity, and sensor systems, marking a key step ahead of her departure to join the fleet at His Majesty’s Naval Base Clyde. The event follows the submarine's official commissioning by King Charles III on September 22, 2025.

Trim Dive and Commissioning

Commander David 'Bing' Crosby, HMS Agamemnon’s commanding officer, explained:
"The trim and basin dive is a key step in the commissioning of HMS Agamemnon. This period enables us to set the boat’s internal weight, prove her watertight integrity, test sensors and put some of our systems through their paces ahead of sailing for the first time."

Pete Tumelty, Astute Programme Director at BAE Systems’ Submarines business, added:
"This trim dive is the culmination of months of hard work. I’d like to thank all teams involved for their commitment and professionalism. We’re incredibly proud of the contribution we’re making to the nation’s security and Barrow’s long and distinguished heritage as the home of UK submarine design and build."

Henry Musgrave, Head of the Astute Delivery Team at the Submarine Delivery Agency, noted:
"The successful completion of HMS Agamemnon’s trim dive marks a pivotal milestone in our mission to safely deliver available and capable submarines to the Royal Navy in defence of our nation. This achievement reflects the exceptional collaboration between the SDA and our partners across the Defence Nuclear Enterprise."

Specifications and Capabilities

• Length: 97 metres

• Displacement: 7,400 tonnes

• Propulsion: Rolls-Royce PWR2 nuclear reactor, providing essentially unlimited range, limited only by crew provisions

• Crew: 98 personnel

• Armament: 6 x 533 mm torpedo tubes, up to 38 weapons, including Tomahawk Land Attack Cruise Missiles (range ~1,000 miles) and Spearfish heavyweight torpedoes

The submarine can operate across a variety of roles, including strategic deterrence, intelligence gathering, and supporting carrier strike groups.

Construction and Program Details

HMS Agamemnon is the sixth of seven Astute-class submarines being constructed by BAE Systems under a £1.4 billion contract. Alongside Astute-class builds, BAE Systems is constructing four Dreadnought-class submarines, the future replacements for the Vanguard-class boats that currently deliver the Continuous At Sea Deterrent (CASD). The Dreadnought-class is expected to enter service in the early 2030s. Design work is also underway on future AUKUS nuclear-powered attack submarines in partnership with the UK, US, and Australia.

BAE Systems Workforce Growth

To support the busy submarine program and growing order book, BAE Systems’ submarines workforce has expanded from 10,700 employees in 2023 to 15,000 today. This is projected to reach 17,000 in the coming years, reflecting the company’s long-term commitment to UK submarine capabilities.

Strategic Importance

HMS Agamemnon’s commissioning strengthens the Royal Navy’s operational readiness and nuclear deterrent capabilities, ensuring at least one submarine is deployed continuously at sea, safeguarding the nation’s security. The successful trim dive confirms that the submarine is ready to progress toward sea trials and eventual full operational deployment.