HMS Agamemnon reaches Clyde after first dive at sea

HMS Agamemnon, the Royal Navy’s sixth Astute-class nuclear-powered attack submarine, arrived at HM Naval Base Clyde in Scotland on 2 October after making its first dive at sea. The arrival followed a voyage from BAE Systems’ Barrow-in-Furness shipyard and marks another stage in the trials that must be completed before the submarine joins the operational fleet.

The boat left Barrow on 25 September with a crew of about 100. Its sea dive took place in the Inner Hebrides exercise areas under the watch of a Royal Navy Merlin helicopter, the Royal Navy said in its account of the arrival. A trim dive to about 15 metres had already taken place in October 2025 at the Barrow shipyard; the Inner Hebrides dive was its first in open water.

Agamemnon’s keel was laid in July 2013, and King Charles III attended its commissioning on 22 September 2025. Commander John Gabb, its commanding officer, described the first sea dive as a significant step in generating a submarine for operations. He said the Merlin that supported this dive would later help train the crew by simulating an adversary, testing the boat’s ability to remain undetected.

Rear Admiral Andy Perks, the Royal Navy’s Director Submarines, said the boat was beginning a demanding programme of sea trials and operational preparation. Performance, manoeuvrability, speed and seaworthiness will be tested over the coming weeks and months. Its arrival at Clyde coincided with the 125th anniversary of the launch of Holland 1, the Royal Navy’s first submarine.

The Astute-class fleet

The Astute class is the largest class of attack submarines operated by the Royal Navy. The boats displace 7,400 tonnes and measure 97 metres in length. Their Rolls-Royce nuclear reactors are designed to operate for the vessels’ service lives without refuelling, according to the UK Ministry of Defence.

The class carries Spearfish heavyweight torpedoes and Tomahawk IV land-attack missiles, which the ministry says can reach targets more than 1,000 miles away. It was also the first Royal Navy submarine class to dispense with optical periscopes in favour of video technology for viewing the surface.

Five Astute-class boats—Astute, Ambush, Artful, Audacious and Anson—are already in service. The seventh and final vessel, HMS Achilles, remains under construction at Barrow. Agamemnon will join the operational fleet after completing its trials.