Inside UK's four Vanguard-Class submarine - including £6billion underwater nuclear monster

Inside UK's four Vanguard-Class submarine - including £6billion underwater nuclear monsterFew people beyond the Prime Minister know exactly where the Vanguard submarine is at any one time, as it has to be one of the British military’s most closely-guarded secretsCommentsNewsChris Hughes Defence and Security Editor12:00, 19 Apr 2026Updated 12:00, 19 Apr 2026View 5 ImagesSnapshot of why the Vanguard fleet is formidable At any moment, a silent and deadly, dark underwater monster is gliding through the depths beneath the world's oceans, its payload capable of unleashing absolute horror thousands of miles away.‌This is the Vanguard-Class ballistic submarine, carrying the UK’s nuclear deterrent, a sleek-looking 25mph leviathan that lurks in the oceans to give Britain the ultimate protection. Today’s prices put the value of the vessel at £6billion - the deadliest maritime weapon the Royal Navy has ever pointed towards Britain’s enemies.‌For decades Britain’s four Vanguards have taken it in turns to slip beneath the waves from their base in Scotland, setting off on secret missions of sometimes six months long. Last year HMS Vanguard returned to base after being on patrol for a record 204 days - the UK’s longest-ever nuclear sub’ deterrent stint as missions have become longer in recent years.‌This operation broke previous records for the UK's Continuous At-Sea Deterrence - CASD- patrols, which are increasingly exceeding five to six months in duration. It may be that the missions are becoming longer because of the threat level increasing around the globe, or that the four subs are taking longer to maintain whilst in dock.View 5 ImagesThe Royal Navy's 16,000 ton Trident-class nuclear submarine Vanguard(Image: PA)READ MORE: UK foiled Russia submarines threats on undersea internet and energy cablesREAD MORE: Iran war ramping up the risk of terrorism in UK - arson and drone attacksAnd the permanent patrols, somewhere in the world’s oceans, costs the UK a stagg...