Three Vanguard Submarines at Sea: Britain’s Deterrent Has No Boat Left Ashore

On 12 October a Vanguard-class boat sailed again after a stop at the Coulport explosives jetty, and two days later another left Faslane, putting three of Britain’s four nuclear submarines at sea at once.

The Times, which first reported the deployment on 27 October, called the concentration unusual, and its navy source went no further than that word. Army Recognition, reporting The Times’ account, names the three boats as Vanguard, Vigilant and Vengeance, with Victorious in deep maintenance at Devonport. No Vanguard-class boat remains alongside. The three at sea are every hull Britain has available, and the fourth sits in 9 Dock at Devonport in a £560 million deep maintenance period. Only one of the three carries the armed deterrent patrol. A second is working up to relieve it, and the third is on sea trials or work-up, according to Navy Lookout’s reading of the movements.

The boat that left Faslane on 12 April had been away 199 days when Navy Lookout counted on 28 October. The patrols stretched because the rotation had been running on two boats. Nine consecutive patrols ran longer than five months. The two before this one ran 203 days and then a record 205 days. The second ended on 18 April, when Vanguard returned to Faslane with the prime minister and the defence secretary aboard for the final part of the homeward journey. The class was designed for patrols of two months, extended to three, with four months as the maximum, according to Warsight. Admiral Sir Tony Radakin, the former chief of the defence staff, said: “There is something wrong when sailors are having to put to sea for extraordinarily long patrols in complex machines beyond their original design life.” In the House of Lords in January, a serving member of the armed forces told ministers that harmony guidelines, the balance between time at sea and time at home, are vital for retention, and the minister replied that they remain a priority for the Government.

Vanguard, commissioned in 1993, is the oldest of the four, and Vengeance, commissioned in 1999, is the youngest. All four were built at Barrow-in-Furness between 1986 and 1999 against a 25-year design life, which puts the class at 27 to 33 years in service. Each boat displaces 15,900 tonnes submerged, measures 149.9 metres, carries a crew of about 135 and has 16 missile tubes. Under the 2010 defence review each patrol boat declared no more than eight missiles and 40 warheads. Since 2021 Britain has published no per-boat numbers, and Army Recognition puts the total stockpile at an estimated 225 warheads against a ceiling raised from 180 to 260 in March 2021.

Victorious is in 9 Dock at Devonport, in the deep maintenance period Navy Lookout describes as extending her life into the 2030s. Her sister Vanguard shows what a long refit costs the rotation. An overhaul planned for three and a half years lasted nearly seven, with the boat rededicated at Devonport in August 2022 and back at sea in May 2023, after a February 2023 investigation into reactor coolant-pipe insulation fasteners reattached with adhesive rather than replaced. The other Vanguard boats were not refuelled during their remaining service lives as a consequence. Faslane’s shiplift gives Vanguard boats priority, and one other Devonport dry dock serves attack submarines until the 10 Dock upgrade completes in 2027, according to Warsight’s account of the yard system. A new non-tidal berth and a refurbished 10 Dock sit under the SWIF programme, whose contract with Babcock was signed in November 2023, while floating dry docks under Programme Euston remain in the concept phase and are unlikely before the early 2030s. A June 2026 survey reported all five in-service Astute-class attack submarines alongside at once, with £500 million of maintenance undone. A 100-day Submarine Maintenance Recovery Plan launched on 15 January 2026 was meant to quicken maintenance delivery.

On 20 April, observers sighted a French Suffren-class attack submarine inbound to the Clyde, and Warsight’s reading is that the French boat escorted Vanguard’s replacement out to sea because no Royal Navy Astute was available for the task. Six months later, on 20 and 21 October, RAF Typhoons escorted French Rafales on a simulated nuclear strike over the Mediterranean in Exercise Rummy, the first time British aircraft have joined a French nuclear air exercise, under the Northwood Declaration. The exercise involved no nuclear weapons, and the government’s release puts £63 billion of nuclear investment over four years behind Dreadnought, the SSN-AUKUS boats and a new warhead, plus 12 F-35A aircraft for NATO’s nuclear mission. Defence Secretary Wes Streeting said: “This exercise marks a new chapter in the defence nuclear relationship between the United Kingdom and France.” Catherine Vautrin, the French minister of the armed forces, said: “Having independent nuclear forces does not exclude coordination.” Navy Lookout finds no evidence connecting the submarine movements to Rummy. The Ministry of Defence, declining operational detail, calls the deterrent “the cornerstone of our national security, protecting the UK and our NATO allies every day, at every moment”.

The replacement programme costs £41 billion, Parliament’s record says, with £31 billion for the build and a £10 billion reserve. The first Dreadnought boats are expected in service in the early 2030s, and Navy Lookout’s April analysis put the first patrol no earlier than about 2032. The four Dreadnought boats, named Dreadnought, Valiant, Warspite and King George VI, will keep the four-boat structure, and Parliament approved the programme in July 2016 by 472 votes to 117. The 2025 defence review committed £15 billion to the sovereign warhead programme by the end of this Parliament. Until the first Dreadnought patrol, the rotation has to be held by boats already past their design lives, with Victorious still in dock.

The Dreadnought boats will displace about 17,200 tonnes submerged. They will carry 12 missile tubes each, against the Vanguard boats’ 16.