The three-day trim dive is a critical commissioning milestone designed to test the 97-meter-long, 7,400-tonne submarine’s balance, buoyancy, and safety systems. It follows the vessel’s formal commissioning by King Charles III earlier this year and marks one of the final steps before the submarine departs Barrow to join the Royal Navy’s fleet at His Majesty’s Naval Base Clyde.
“This trim dive is the culmination of months of hard work,” said Pete Tumelty, Astute Programme Director at BAE Systems Submarines. “I’d like to thank all teams involved for their commitment and professionalism.” Commander David ‘Bing’ Crosby, the Commanding Officer of HMS Agamemnon, described the exercise as a vital phase in ensuring operational readiness:“This period enables us to set the boat’s internal weight, prove her water-tight integrity, test sensors, and put some of our systems through their paces ahead of sailing for the first time. It takes a great deal of planning and preparation to achieve this key step and all involved should be very proud of the part they have played.”
The Astute-class program includes seven submarines, with HMS Agamemnon being the sixth under construction at BAE Systems. Alongside this program, the company is also building four Dreadnought-class submarines, which will replace the Royal Navy’s current Vanguard-class boats that deliver the Continuous At-Sea Deterrent (CASD). The Dreadnought vessels are expected to enter service in the early 2030s. Henry Musgrave, Head of the Astute Delivery Team at the UK’s Submarine Delivery Agency (SDA), said: “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. This achievement reflects the collaboration between the SDA and our partners across the Defence Nuclear Enterprise, demonstrating our commitment to supporting the UK’s nuclear deterrent.”In parallel, BAE Systems continues design work on future AUKUS-class nuclear-powered attack submarines, being developed jointly by the United Kingdom, the United States, and Australia. The company’s submarine workforce has grown from 10,700 in 2023 to 15,000 in 2025 and is projected to reach 17,000 in the coming years, supporting ongoing and future programs.