Up until the 1990’s you could set off the British nuclear arsenal with a bike lock-key:
Unbelievable:
PALs (Permissive Action Links) were introduced in the 1960s in America to prevent a mad General or pilot launching a nuclear war off their own bat - the Dr Strangelove scenario.
And this was apparently all you needed to do if you were any British soldier wanting to set off WW3:
To arm the weapons you just open a panel held by two captive screws - like a battery cover on a radio - using a thumbnail or a coin.
Inside are the arming switch and a series of dials which you can turn with an Allen key to select high yield or low yield, air burst or groundburst and other parameters.
The Bomb is actually armed by inserting a bicycle lock key into the arming switch and turning it through 90 degrees. There is no code which needs to be entered or dual key system to prevent a rogue individual from arming the Bomb.