I had no idea - thank you :)

>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.

https://web.archive.org/web/20120311235156/http://news.bbc.c...

http://www.liveleak.com/view?i=4ad_1227686113&comments=1

I like to believe it's the same bike locks that could be defeated with a ballpoint pen:

https://en.wikipedia.org/wiki/Kryptonite_lock

Ah, thank you. Some faulty bits in my memory caused an early nul termination.