This Scalextric-like trigger is the "big red button" politicians fear ever having to use, unless they're Jeremy Corbyn, who has pledged he never will.
The trigger held by Lt Cdr Woods
This rarely-seen Weapons Engineer Officer's Tactical Trigger would be used in the final stage of a Trident missile launch, unleashing nuclear armageddon.
It is pictured aboard HMS Vigilant, one of four nuclear warhead-carrying submarines, ahead of a visit by Defence Secretary Michael Fallon.
Lt Cdr Woods, the weapons officer who would pull the trigger in the event of the unthinkable, told The Telegraph: "It is a combination of an honour and a burden.
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"We have to act on the orders of our lords and masters. When you are at sea on a submarine, you don't know the whole story and you have to trust they know what they are doing.
"The Trident is ultimately a political weapons system. It is there as a deterrent. If we are in the position of launching it, then ultimately deterrence has failed."
Fallon's visit also saw a rare glimpse of the safe containing David Cameron's letter of last resort, something each prime minister hand-writes for submarine crews to be read only in the event of a nuclear launch.
Daniel Martyn, commanding officer of HMS Vigilant, next to a safe that contains the Prime Minister's last resort instruction
Fallon said: "Around the clock nuclear deterrent is as crucial to Britain’s defence now as it has ever been. It is the ultimate guarantee of the nation’s security.
We use our nuclear deterrent every day to deter a nuclear attack, nuclear blackmail and extreme threats that cannot be countered by any other means."
The Red Button: Inside A Nuclear Sub
Corbyn's pacifist stance and desire for nuclear disarmament has caused tension within the Labour party. Corbyn recently suggested Trident submarines could sail without nuclear warheads, prompting mocking attacks from the Conservatives.