Key facts
- HMS Vengeance spent 217 days submerged, surpassing the previous 205-day record set by the prior crew.
- The Vanguard class was designed for three to four months of food for a crew of about 140.
- David Cullen of the Basic thinktank said the fleet was designed around three-month tours.
- Labour blamed Conservative spending cuts for slow submarine maintenance; naval chiefs said there is a plan for improvement.
- HMS Dreadnought, the first replacement for the four Vanguard submarines, is not expected until about 2032.
- Labour announced a £26bn, 10-year plan in July to invest in Faslane, Devonport and Portsmouth naval bases.
HMS Vengeance returned to Faslane naval base in Scotland on November 15, 2026, after 217 days submerged, the longest patrol by a Trident submarine. The boat began its deployment on April 12, surpassing the previous 205-day record set by the prior crew.
The Vanguard class was designed to carry three to four months of food for a crew of about 140, and deployments of more than 100 days were considered highly exceptional when the submarines entered service in the 1990s. Missions now start with tinned food crammed into corridors and other available spaces.
David Cullen, a nuclear expert with the Basic thinktank, said: "Patrols are getting longer and longer. The fleet was designed around three-month tours, and that was considered to be a long time to be stuck underwater in a metal box with no contact with the outside world."
The increase in time at sea reflects the slow pace of submarine maintenance, prompting Labour to blame spending cuts implemented by the Conservatives, though naval chiefs insist there is a plan for improvement. Last week, the head of the Royal Navy, Gen Sir Gwyn Jenkins, said he had "nothing but tremendous respect" for the Trident sailors, but added that the UK needed to "improve our submarine maintenance" to allow faster turnaround.
HMS Vengeance is one of four submarines responsible for carrying Britain's Trident nuclear missiles. At any time a boat is at sea, so the UK could launch strikes even if Britain had already been destroyed in a nuclear war. Each submarine has to keep its location secret so it cannot be targeted, meaning it also cannot be resupplied.
In July, Labour announced a £26bn, 10-year plan to invest in Britain's three main naval bases, at Faslane, the operational home of the Trident submarines, Devonport and Portsmouth, as part of a wider increase in defence spending. However, the first of the replacements for the four Vanguard class submarines, HMS Dreadnought, is not expected to be ready until about 2032, meaning that the old boats have at least five more years to remain in service.