Behind the scenes on a nuclear submarine

 Trident subs are 30 yards longer than a football pitch

Beneath the oceans of the world, somewhere, silently and undetected, lies a British submarine carrying 16 nuclear tipped ballistic missiles and up to 160 men.

Its role is very straightforward: to maintain a constant readiness to unleash nuclear retaliation if the order ever comes.

The aim: to deter any pre-emptive attack on the United Kingdom.

The Royal Navy has four of these Vanguard class boats and one always has to be cruising the depths to provide a "continuous at-sea deterrent", the argument being that a weapon based on land would be too vulnerable to a surprise attack.

The vessels themselves are huge. Thirty yards longer than a football pitch, or 18 double-decker busses long.

 

HMS Vengeance is part of the United Kingdom's independent Nuclear deterrent, armed with 16 Trident II D-5 missiles carrying nuclear warheads of varying firepower.

Elite crew

But if the technology of both submarine and missiles are remarkable and very different from other branches of armed forces, then so is the crew.

They see themselves as the Navy's elite, the Dolphins on their uniform as prized as a paratrooper's wings.

As they rehearse their launch drill, the uniqueness of their role in the British armed forces becomes apparent as the guardians of the nation's nuclear arsenal.

Virtually incommunicado for three months at a time, each sailor receives only two 60-word "family grams" a week to which he cannot reply.

(@BBC)