I recall a stand-off between Thames Valley Police and armed USAF police when a new officer decided to have all civilian traffic on the main road stopped and the drivers checked. He became decidedly undiplomatic when told by TVP that he had no authority to do this and was committing an offence, as well as being invited to copulate hence by the drivers. Eventually, he was reigned in by his boss.
We used to know a US civilian employee who had access to Heyford PX. Helped furnish the house at a whopping discount!