We had a member at a certain airfield down south that no longer exists, who used to come in and hire an a/c every couple of weeks on a Saturday.
He seemed a nice chap who kept himself to himself. It turned out that he was flying a couple of miles off shore and scouting for customs and police so that the drug boats could hit the beach without interference......!
That was only part of it though, he ended up being done for murder after the Essex Range Rover murders.