HMS Agamemnon, the Royal Navy's sixth Astute-class attack submarine, sailed from BAE Systems' shipyard in Barrow-in-Furness to begin sea trials, the Ministry of Defence and Defence Nuclear Enterprise said in a 25 September 2026 release. The conventionally armed, nuclear-powered submarine is 97 metres long and weighs 7,400 tonnes, according to the release, and is powered by a Rolls-Royce Submarines reactor built in Derby.

The ministry said the submarine would be armed with Spearfish torpedoes and Tomahawk IV land attack missiles able to strike targets at a range of more than 1,000 miles. First Sea Lord General Sir Gwyn Jenkins said in the release that she had begun sea trials and would soon arrive at HMNB Clyde to join the fleet. The release states HMS Agamemnon was formally commissioned by the King at a ceremony on 22 September 2025.

The release cites £6 billion of government investment in the submarine industrial base over the Spending Review period, and £47 billion for submarine build programmes within a £298 billion Defence Investment Plan over four years. It says more than 14,000 roles in Barrow are supported by defence nuclear work and that the Defence Nuclear Enterprise supports over 47,000 jobs across the UK.