HMS Agamemnon Completes First Submersion in Major Milestone for Royal Navy

The UK’s newest nuclear-powered submarine, HMS Agamemnon, has successfully submerged for the first time during testing at BAE Systems’ shipyard in Barrow-in-Furness.

The milestone, known as a “trim dive,” marked a key phase in preparing the 97-metre, 7,400-tonne Astute-class attack submarine for active service. Over a three-day period in the Devonshire Dock, Royal Navy crews conducted a series of stability and safety trials to ensure the vessel’s systems and balance performed as expected underwater.

This achievement follows closely after King Charles III formally commissioned HMS Agamemnon into the Royal Navy fleet, placing it one step closer to joining its sister submarines at His Majesty’s Naval Base Clyde in Scotland.

“This trim dive is the culmination of months of hard work. I’d like to thank all teams involved for their commitment and professionalism,” said Pete Tumelty, Astute Programme Director at BAE Systems Submarines. “We’re incredibly proud of our contribution to national security and to Barrow’s long-standing legacy as the heart of UK submarine design and construction.”

Commanding Officer Commander David ‘Bing’ Crosby praised his crew and partners for reaching this critical phase.

“The trim and basin dive is a vital step in bringing HMS Agamemnon to life,” he said. “It allows us to set the submarine’s internal balance, confirm her water-tight integrity, and rigorously test sensors and onboard systems before she sails for the first time. This success is a testament to meticulous planning and the dedication of everyone involved.”

HMS Agamemnon prepared for the first dive

HMS Agamemnon is the sixth vessel in the Astute-class series of submarines, with one more still under construction at BAE’s Barrow facility. Alongside this program, the company is also building four Dreadnought-class submarines in collaboration with the wider Defence Nuclear Enterprise.

The Dreadnought-class boats will replace the current Vanguard-class fleet, which has maintained the UK’s Continuous At Sea Deterrent (CASD) for over five decades. The first of these new vessels is expected to enter service in the early 2030s, ensuring the UK’s nuclear deterrent capability continues without interruption.

Henry Musgrave, Head of the Astute Delivery Team at the Submarine Delivery Agency, called the trim dive a defining achievement:

“The successful completion of HMS Agamemnon’s trim dive represents a major step forward in delivering capable submarines to the Royal Navy. It highlights the strong collaboration across the Defence Nuclear Enterprise and our shared commitment to safeguarding the nation.”

In addition to the Astute and Dreadnought programs, design work is advancing on a future generation of nuclear-powered AUKUS-class attack submarines, developed under the security partnership between the UK, the United States, and Australia.

To meet growing demand, BAE Systems has significantly expanded its workforce, increasing from 10,700 employees in 2023 to 15,000 today, with projections to reach 17,000 in the near future.

The successful dive of HMS Agamemnon not only reinforces the Royal Navy’s technological edge but also underscores Barrow’s pivotal role in shaping the next era of British submarine engineering.