As pictured:

http://imgur.com/a/yh2lE

This is the locking kind - it locks itself on when you push it on (you don't need the key for that), but always requires the key for removal.

Very good quality, there is no slop in the mechanism at all. PCD is 70 mm to the steering wheel and 75 mm on the steering column side.

Does not come with the horn adaptor plate (this is needed for the horn mechanism to work but the boss can still be used fine without it, this will save you at least 100 grams :-) ). You could make up an adaptor plate fairly easily with a lathe, I would think.

£75 posted (or collect from Cambridge area).