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