For more than 50 years, there has always been at least one Royal Navy submarine patrolling beneath the waves armed with a nuclear missile. The Continuous At Sea Deterrent, known as Op Relentless, is the UK’s longest ever sustained military operation, and while nuclear weapons are controversial, it is a vital part of British defence.
Britain’s Trident nuclear deterrent missiles are carried by four ageing Vanguard-class submarines: HMS Vanguard, Vengeance, Victorious and Vigilant. The almost 150-metre boats entered service in the 1990s with an initial service life of 25 years and have been undergoing life extension programmes. The submarines have been Britain’s only nuclear weapon capability since 1998; however, the Government has now announced plans to purchase F-35A stealth fighter jets, which can fire tactical nukes.
These are less powerful than Trident, which is a strategic nuclear weapon that makes up a concept known as mutually assured destruction — the highest level of deterrence against adversaries such as Russia, which often makes nuclear threats.
The Trident deterrent is operationally independent, but the missiles are US-built and the system does rely on the US for maintenance.
Each Vanguard-class submarine can carry 16 Trident missiles, which cost around £17 million each, and can be fired at targets up to 4,000 miles away.
The weapon was introduced in 1994 and it emerged last year that a Trident test fire off the coast of Florida failed.
Defence officials at the time said “absolute confidence” remained in the weapons system, which has completed more than 190 successful tests.
The UK is estimated to have around 225 nuclear warheads — fewer than France (around 300) and considerably fewer than Russia and the US (more than 5,000 each).
The Vanguard-class are nuclear-powered, meaning they effectively have an unlimited range.
Patrols of the boats have been increasing in recent years — notably HMS Vanguard’s record 204-deployment which was completed this year — amid reported issues around maintenance.
There have been concerns that the longer deployments could lead to a rise in personnel leaving the Silent Service, with the wider military facing a recruitment and retention crisis.
The Navy has been looking into teaching submariners top sport psychology techniques to improve mental resilience amid the increasingly lengthy deployments.
The Vanguard-class submarines have a crew of around 130, with most submariners working for six hours on, six hours off and no days off.
Crews go months with no access to sunlight or fresh air as they carry out their top-secret patrols.
The Vanguard-class are set to be replaced by the Dreadnought-class from the early 2030s.
In March, the Prime Minister Sir Keir Starmer laid the keel of the first boat in Barrow-on-Furness, where it will be built.
Clyde naval base, also known as Faslane, is the home of the submarines and nuclear deterrent.
The Navy also has Astute-class hunter-killer submarines, which are nuclear-powered but conventionally armed.
The arrival of the new F-35As for the Royal Air Force means the UK will have an air-launched nuclear capability for the first time since the late 1990s.
