Sea vessels

Navy's fifth Astute-class submarine one step closer to entering service

The Royal Navy's next attack submarine is one step closer to entering service after completing a major milestone.

HMS Anson was submerged completely in a 'trim dive' at Devonshire Dock in Barrow.

Crew tested onboard systems were water-tight, as well as other capabilities.

The 7,400-tonne, 97 metre-long HMS Anson is the Navy's fifth Astute-class submarine - four of the seven other vessels are already in service.

Commanding Officer of Anson, Commander David 'Bing' Crosby, said: "The trim and basin dive is a key step in the commissioning of HMS Anson.

"This period will enable us to set the boat's internal weight, prove her water-tight integrity, test sensors and put some of our systems through their tests ahead of sailing for the first time."

A 'trim dive' is essential to help engineers establish the vessel's centre of gravity and precise weight, with more than 60 crew members and tonnes of ballast on board to help test stability.

HMS Astute, HMS Artful, HMS Ambush and HMS Audacious are the other Astute-class subs to have gone through similar testing before commissioning into the Royal Navy.

HMS Anson during the trim dive (Picture: BAE Systems).

HMS Anson is set to be the fifth in line and, the final two, HMS Agamemnon and HMS Agincourt, are at different stages of construction at the Barrow shipyard.

The Astute-class submarines will replace the Trafalgar-class.

They are the biggest and quietest attack submarines ever constructed for the service, carrying Tomahawk Land Attack Cruise Missiles (TLAM) and Spearfish heavyweight torpedoes.

Capable of producing their own oxygen and drinking water, they can circumnavigate the globe while submerged.