Navy News
Direct from the front-line, the official newspaper of the Royal Navy, Navy News, brings you the latest news, features and award winning photos every month.
Historic science merges with latest tech to perfect Navy’s newest submarine’s maiden dive
13 October 2025
18th Century techniques and modern engineering helped pave the way for the safety and success of the Royal Navy’s most-advanced submarine as HMS Agamemnon performed her maiden dive.
The hunter-killer, which was commissioned last month in the presence of His Majesty the King, is the first line of defence for the UK’s nuclear deterrent and aircraft carrier task groups against hostile submarines.
Awesome Aggie, as crew call her, conducted a test dive in Barrow, one of the final acts in her construction before she joins the Silent Service, submerging in a special basin at BAE System’s facility.
Known as a ‘trim dive’, it is used to assess the submarine’s stability and pinpoint her centre of gravity, with scientists, naval architects and engineers taking detailed measurements and readings on board.
Some of Agamemnon’s other systems are also tested while submerged, not least blowing the ballast tanks which ensure the boat can surface.
Huge though the dive basin is, it is not deep enough to completely swallow an Astute-class submarine. Agamemnon dived 15 metres (49ft), covering all the boat except for her fin.
Joining 30 crew members onboard – led by Commanding Officer Commander David ‘Bing’ Crosby, who guided HMS Anson through the same process back in 2022 – for the milestone evolution were BAE engineers, experts from across the Submarine Delivery Agency and naval architects.
They brought with them 16 tonnes of lead weights, which they moved from side-to-side on trolleys, to establish Agamemnon’s centre of gravity.
As a backup, the movement is still measured by hand using pendulums hung between decks – a method used by naval architects since the 1700s, although modern inclinometers are used to record the submarine’s motion throughout.
I would like to thank all for their support on this achievement. After a fabulous commissioning ceremony with His Majesty, the completion of a trim dive and main steam testing shows real momentum towards taking her to sea.
The results also calculate the precise weight and stability, determining how the sixth (of seven) Astute-class submarines will perform in-service.
On the second day the submarine conducted numerous dives and tested all surfacing techniques as well as un-staffed runs for the escape systems.
“This is a key milestone on Aggie’s drive to exit – the culmination of months of joint enterprise work to safely and successfully undertake this event,” said Commander Crosby.
“I would like to thank all for their support on this achievement. After a fabulous commissioning ceremony with His Majesty, the completion of a trim dive and main steam testing shows real momentum towards taking her to sea.
“There is much still to do but the joint working will enable us to clear our final tests and exit Barrow.”
Henry Musgrave, Head of Astute Delivery Team at the Submarine Delivery Agency, praised the “unwavering commitment” of everyone involved in the programme to reach this pivotal milestone in the boat’s construction.
“As HMS Agamemnon moves closer to joining the operational Astute-class fleet, this achievement showcases the world-leading expertise and dedication of our teams at the Submarine Delivery Agency and BAE Systems. Together, we continue to build the most advanced and powerful attack submarines ever operated by the Royal Navy.”
Further trials, tests and training are lined up for Aggie and her 100 crew, preparing the submarine for her maiden voyage to HM Naval Base Clyde to begin training ahead of operational patrols.