HMS Agamemnon arrives at Faslane to begin sea trials after 13 years of building

What happened

HMS Agamemnon, the Royal Navy's newest nuclear-powered attack submarine, has arrived at its home port of Faslane in Scotland to begin an extensive programme of sea trials.

The 97-metre hunter-killer vessel reached HM Naval Base Clyde on 2 October after sailing from BAE Systems' shipyard in Barrow-in-Furness, Cumbria, on 25 September. During its transit, the submarine completed its first-ever dive in the waters of the Inner Hebrides, monitored by a Royal Navy Merlin helicopter.

Why it matters

The arrival of the 7,400-tonne submarine marks the end of an exceptionally long construction period. Agamemnon’s keel was laid in July 2013, with defence officials originally expecting it to enter service by 2022. It was eventually commissioned by King Charles III on 22 September 2025, but spent another full year at the shipyard undergoing reactor tests and final preparations.

Its first voyage also ends an unusual four-month gap during which no British attack submarines were at sea. The Royal Navy's only recently active Astute-class submarine, HMS Anson, returned from deployment and docked in Devonport on 27 May 2026. Since then, no active British hunter-killer submarine has been underway.

While Agamemnon is not yet fully ready for combat duties, its departure from the shipyard is a major step toward restoring the fleet's active strength.

What happens next

Over the next year, the submarine’s 100-strong crew will test its capabilities, speed, and weapons systems in deep water.

The vessel is equipped with Tomahawk land-attack cruise missiles and Spearfish heavyweight torpedoes. Its commanding officer, Commander John Gabb, said the initial dive was a major milestone, but explained that future training will push the crew further.

"We will get to know Agamemnon well over the coming months, but this submarine is incredibly quiet, has a world-class Sonar and will be home to us all as we generate for operations," Commander Gabb said. He added that the crew would soon perform pre-operational exercises simulating aerial threats, pushing the submarine "to its maximum potential to operate undetected."

The Royal Navy has not officially disclosed when the submarine will enter active service. However, looking at previous deployments, such as HMS Anson's 15-month transition from leaving the shipyard to full operational readiness, Agamemnon is likely to join active operations in late 2027.

Rear Admiral Andy Perks, the Royal Navy's director of submarines, welcomed the vessel's arrival, calling it a "significant milestone" made possible by thousands of workers across the UK's defence nuclear sector.

Agamemnon is the sixth of seven planned Astute-class submarines, joining HMS Astute, Ambush, Artful, Audacious, and Anson at the Clyde naval base. The final submarine in the class, HMS Achilles, remains under construction in Barrow.