HMS Agamemnon departs Barrow after 13 years to begin Royal Navy sea trials

The Royal Navy’s sixth Astute-class attack submarine, HMS Agamemnon, has left BAE Systems’ Barrow-in-Furness shipyard for the first time, more than 13 years after construction began.

The 97-metre, 7,400-tonne submarine travelled through the shipyard’s docks into the Walney Channel and the Irish Sea. She will head to HM Naval Base Clyde and undergo sea trials before joining the five Astute-class boats already in operational service.

Agamemnon’s keel was laid in July 2013, when the Ministry of Defence expected her to enter service in 2022. King Charles III formally commissioned her in September 2025, but the boat remained at Barrow for further testing, including her first dive the following month.

HMS Agamemnon to enter sea trials

Agamemnon will now undergo sea trials before joining HMS Astute, HMS Ambush, HMS Artful, HMS Audacious and HMS Anson in operational service. According to Navy Lookout, she will also need to complete weapons testing and crew training. Based on the experience of HMS Anson, that process could take around 12 to 15 months, although the MoD has not given an operational date.

The Astute class has several roles beyond attacking enemy ships and submarines. The MoD says the boats gather intelligence, protect maritime task groups and support the UK’s continuous at-sea nuclear deterrent. Agamemnon is nuclear-powered but conventionally armed, carrying Spearfish heavyweight torpedoes and Tomahawk land-attack missiles.

BAE Systems Submarines managing director Steve Timms said the departure “demonstrates the growing momentum underpinning our submarines business”. For the Royal Navy, the more consequential milestone will come when Agamemnon completes her trials and is available for operations.

Three submarine programmes at Barrow

The UK submarine industry is now working across three classes. The seventh and final Astute-class boat, HMS Achilles, is at an advanced stage of construction at Barrow. BAE Systems is also building all four Dreadnought-class ballistic missile submarines, which will replace the Vanguard class in carrying the UK’s nuclear deterrent.

Preparations are under way for SSN-AUKUS, the next-generation attack submarine that will eventually replace Astute. Steel is expected to be cut for the first UK boat in 2027, while the government is investing in the industrial capacity needed to work towards building one SSN-AUKUS submarine every 18 months. The eventual number of boats has yet to be decided.

The MoD says defence nuclear work supports more than 14,000 roles in Barrow. Agamemnon’s departure frees one boat from the shipyard’s programme, but Barrow must continue building Achilles and Dreadnought while preparing its workforce and facilities for SSN-AUKUS.