There is the apocryphal story of the very junior RAF Regiment officer, newly graduated from Cranwell, who was sent to Buckingham Palace when the QCS carried out changing of the guard for a couple of weeks. Needless to say, he took along his mess kit as ordered, and found himself at Dinner with the family (it was customary for the off duty guard commander to dine during the deployment to the Palace). The poor chap knew nothing about horses and corgis and was a little short of conversation so Prince Phillip decided to break the ice:
"Tell me, young man. All of our Army chaps have lots of different uniforms for dining and yet you RAF chaps only seem to have just the one".
" Oh well sir, this is the 5b dress with a soft shirt and blue waistcoat, but we can also wear the 5a dress which has a stiff white shirt with wing collar and a white waistcoat - but we only wear that one for special occasions..."
Cue an explosion of laughter into the soup.