I recall a tale from the early 80's at West Drayton. In the days of no rank slides on the shoulders of the junior ranks (that bit's important). The SWO (possibly the first female one in the RAF) was in the guardroom one day when a young man walked in wearing a light blue shirt under a blue/grey jersey which bore no insignia. He politely asked the duty Cpl for a car pass. Spotting the hatless young man, the SWO erupted, and basically informed him that no car pass would be obtained until he was properly dressed i.e. hat on head. The young man apologized and returned to his vehicle to get his hat. He re-entered the guardroom a few minutes later wearing a hat which resembled the standard RAF SD cap however, the badge on the front of said cap bore the badge of the RAC. Red-faced, the SWO slinked away to the back of the guardroom muttering "Cpl, get this man a car pass."