HMS Agamemnon Explained: Britain's Newest Attack Submarine Reaches Its Clyde Home Port

HMS Agamemnon, the Royal Navy’s sixth Astute-class nuclear-powered attack submarine, arrived at her home port, HM Naval Base Clyde at Faslane, on Friday 2 October 2026. She sailed there from the BAE Systems yard at Barrow-in-Furness, where she was built over more than 13 years. As of 3 October 2026 she is still on sea trials and operational preparation, so this is an arrival, not yet an entry into service.

What is HMS Agamemnon?

HMS Agamemnon (pennant S124) is a nuclear-powered attack submarine, often shortened to SSN, and the sixth of seven Astute-class boats planned for the Royal Navy. “Attack” describes her job of hunting other submarines and ships and striking targets ashore, which is separate from the Vanguard-class boats that carry the UK’s nuclear deterrent. BAE Systems builds the class at Barrow, and Agamemnon is named after the Greek king who led the besiegers of Troy. About 100 submariners crew her, according to the Royal Navy, and her commanding officer, Commander John Gabb, called it “an enormous privilege to be the first person to command this vessel at sea”.

When did HMS Agamemnon arrive at Faslane, and how did she get there?

She arrived at HM Naval Base Clyde on Friday 2 October 2026, roughly a week after leaving the Barrow shipyard. Reports disagree on the exact departure day: BAE Systems’ own announcement is dated 25 September, some defence reporting puts the dock departure on 24 September, and one account describes a two-day operation to work her through Barrow’s docks and the narrow Walney Channel. We therefore say only that she left in the last week of September.

On the passage north she made her first dive at sea, in waters the Royal Navy calls the Inner Hebrides exercise areas. Before that she had done only a trim dive in the Barrow dock in October 2025. Commodore Ben Haskins welcomed her as the newest submarine of the Flotilla, and Rear Admiral Andy Perks, Director Submarines, credited thousands of people across the Defence Nuclear Enterprise with her delivery.

The date also marked 125 years since Holland 1, the Royal Navy’s first submarine, was launched at Barrow on 2 October 1901, a coincidence the Royal Navy’s release highlighted.

What does “home port” mean, and why Faslane?

A home port is the base where a warship is permanently assigned and where her crew and support organisation are based, and for HMS Agamemnon that is HM Naval Base Clyde. The base sits on Gare Loch and Loch Long in Argyll and Bute, roughly 25 miles west of Glasgow. It has two main sites: Faslane, the submarine base on Gare Loch, and the armaments depot at Coulport on Loch Long. The Royal Navy’s submarine flotilla is centred there, so a boat built in Cumbria is delivered to Scotland to join it.

What is an Astute-class submarine?

Astute-class boats are the Royal Navy’s current nuclear-powered attack submarines: about 97 metres long, driven by a Rolls-Royce PWR2 reactor, and armed with Tomahawk land-attack missiles and Spearfish heavyweight torpedoes. Specialist defence reporting puts Agamemnon at about 7,400 tonnes. Other published figures differ, depending on whether a boat is surfaced or submerged or because they are unverified, so we use 7,400 as a round figure.

The Royal Navy and BAE Systems say the class uses video technology in place of optical periscopes and can circumnavigate the globe without surfacing. The Royal Navy’s published description of the role, given when Agamemnon was floated out in October 2024, is protecting the UK’s nuclear deterrent and carrier task groups, gathering intelligence, supporting Royal Marines operations and striking land targets with Tomahawk.

How long did HMS Agamemnon take to build?

Her keel was laid on 18 July 2013 and she left the Barrow yard in late September 2026, a gap of just over 13 years. The main milestones:

A commissioning ceremony is a milestone, not the finish line: she has since had to leave the yard and begin testing at sea. At the 2025 ceremony King Charles III read the commissioning warrant.

Is HMS Agamemnon operational yet?

No. As of 3 October 2026 she is on sea trials and operational preparation, and the Royal Navy says only that she will join the operational fleet in due course. No in-service date has been published, and we are not offering one. One specialist naval news site points to the previous boat, HMS Anson, whose trials ran for more than a year after she left Barrow. That is an outlet’s comparison with a past boat, not a Royal Navy timetable for Agamemnon.

How many Astute-class submarines are there?

Seven are planned: five are in service, HMS Agamemnon is on trials, and a seventh and final boat is under construction. The five in service are Astute, Ambush, Artful, Audacious and Anson. The seventh, HMS Achilles, is being built at Barrow, according to the Royal Navy’s release. That count will change once Agamemnon joins the operational fleet, so check the date at the top of this page before relying on it.

So what has actually changed?

What has changed is her address: HMS Agamemnon is no longer a boat in a Barrow shipyard but a submarine with a home berth on the Clyde. Sea trials and operational preparation still lie ahead, and the Royal Navy has not set out a timetable for them.