BAE Systems has announced the successful completion of the first underwater testing for HMS Agamemnon, the United Kingdom’s newest nuclear-powered attack submarine.
The milestone took place at the company’s Submarines site in Barrow-in-Furness, just weeks after the vessel was formally commissioned into service by His Majesty King Charles III.
According to BAE Systems, the event—known as a trim dive—lasted three days and was conducted in Devonshire Dock in Barrow. The operation tested the submarine’s stability, buoyancy, and safety while submerged, and represents a major technical step toward the boat’s eventual integration into the Royal Navy’s operational fleet.
The company said the exercise is a critical milestone “in the lead-up to HMS Agamemnon’s departure from Barrow to join her sister boats in the fleet.”
The submarine, weighing 7,400 tonnes and measuring 97 meters in length, is part of the UK’s Astute-class program—a long-running project that began with the commissioning of HMS Astute in 2010. BAE Systems builds the boats at its Barrow yard, which remains the hub of the UK’s submarine manufacturing capability.
HMS Agamemnon was officially welcomed into Royal Navy service during a commissioning ceremony on 22 September 2025, hosted at the Barrow shipyard. His Majesty King Charles III presided over the event, marking the formal entry of the sixth Astute-class submarine into the fleet.
The Astute-class submarines are designed to combine high-endurance patrol capabilities, stealth, and precision firepower. They are armed with Tomahawk Land Attack Missiles and Spearfish heavyweight torpedoes, and are engineered to operate globally without surfacing for extended periods.
For the Royal Navy, HMS Agamemnon is expected to play a critical role in securing the UK’s undersea advantage amid a more complex global maritime environment.
As noted by BAE Systems, the vessel’s recent underwater trials underscore the Royal Navy’s continued investment in next-generation deterrence and sea power.
The submarine is now moving into the final phase of testing and outfitting before sea trials begin. Once operational, it will join the rest of the Astute-class fleet, which includes HMS Astute, Ambush, Artful, Audacious, and Anson—with a seventh and final boat, HMS Achilles (ex Agincourt), currently under construction.