Ahah, sorry.
If you are referring to an Al-Ko wheel lock, they dont have a bolt in the receiver, they have a yellow plastic cap slotted for a screwdriver. Perhaps a previous owner has lost the cap and put a standard bolt in. If its a hexhead, and socket with enough reach would do it. If its got a fancy recessed head, you would need the special tool that is UNIQUE to your own lock. These locks are registered at Al-Ko and as long as you are on the database, they would supply a replacement. If you have the full wheel lock kit, look inside it for a longish piece with a hex head at one end and a matching machined recess at the other.
The following link shows the proper alko bolt and removal tool, it may help
http://www.inglewoodleisure.co.uk/wheel-locks-and-accessories/342-al-ko-replacment-locking-bolt.html