Apparently KAR120C was the number on the original car used in The Prisoner (there were several different ones used, apparently), which was supplied by the then Lotus distributor Caterham Cars (who later bought the design license), owned by Graham Nearn. The number apparently stayed with Caterham cars, being fitted to a string of demonstrators, and is still retained by Graham Nearn.

I dread to think what kind of money would be required to persuade him to give it up !

Nick