HMS Agamemnon, the Royal Navy’s sixth Astute-class attack submarine, has left BAE Systems’ yard at Barrow-in-Furness and entered open water for the first time as it begins sea trials ahead of joining the fleet, according to BAE Systems.

The 7,400-tonne, 97-metre submarine moved through the shipyard’s dock system into the Walney Channel before continuing into the Irish Sea. Agamemnon will now undergo a programme of sea trials before joining HMS Astute, HMS Ambush, HMS Artful, HMS Audacious and HMS Anson in Royal Navy service.

Steve Timms, Managing Director of BAE Systems’ Submarines business, said: “The Astute class submarines are equipped with the latest technologies to silently circumnavigate the globe without surfacing, whilst fulfilling a range of tactical roles for the Royal Navy.

“The departure of HMS Agamemnon, the sixth of seven such submarines that we are building here in Barrow, demonstrates the growing momentum underpinning our submarines business and is a proud moment for everyone involved across the UK’s submarine enterprise.”

First Sea Lord General Sir Gwyn Jenkins said Agamemnon would move to HMNB Clyde after sea trials and join the Royal Navy’s operational submarine force. He said: “In an increasingly dangerous world, sea power remains fundamental to keeping our country and people safe. Our submarine fleet is essential to that effort, which is why I am delighted that HMS Agamemnon, the sixth of our Astute-class submarines, has now begun sea trials and will soon arrive at HMNB Clyde to join the fleet.

“She embodies the best of British engineering and the professionalism of our submariners and will be one of the most advanced submarines ever operated by the Royal Navy.

“As we continue to strengthen our warfighting readiness, HMS Agamemnon will play a central role in keeping the United Kingdom safe, contributing to NATO’s collective defence and ensuring we are ready to lead, fight and win.”

Work is meanwhile continuing on Achilles, the seventh and final Astute-class submarine, which BAE Systems said is at an advanced stage of construction. The Barrow yard is also building all four Dreadnought-class ballistic missile submarines which will replace the Royal Navy’s Vanguard-class boats carrying the UK’s nuclear deterrent.

BAE Systems is also carrying out early design and concept work on SSN-AUKUS, the next generation of nuclear-powered attack submarines intended eventually to replace the Astute class. The company and the wider Defence Nuclear Enterprise are expanding infrastructure, technology and workforce capacity at Barrow to support the overlapping Astute, Dreadnought and SSN-AUKUS programmes.