That's right. Wheel bolts ! :-)
I tried the smacking the socket trick, it has worked for me before.
The security bolt has a slight shoulder on the head so it' slightly smaller than the diameter of the rest of it.
When I smacked a socket over it, it seemed to get mangled on the smaller part then just spun around the larger part (not explained that very well). Needless to say it didn't work.
The bolt removal set just arrived - this is the sort that is reverse-threaded and is supposed to cut it's way onto the bolt head as it tightens then out comes the bolt
Didn't even scratch it so that's going back and I've ordered a toughened smack-on type remover.
Getting no-where fast with this one. When I finally get unfettered access to the crank pulley, I'll report back!!