One of our more prickly Air Engs, known as 'Caring Ken, the Airman's friend' ("Take your hands out of your pocket when you're talking to my Captain, airman!") was once staying at some pongo mess. After a long day, he too was given the usual ignoring by the barman, but inquired as to the reason. He was told that the RSM had to be served first, or some such tradition.
Not to be outdone, Ken replied that he was senior to the RSM (true) and would like a beer. With which he was then served.
Enter the RSM and cronies in full "What's going on here then" mode. Caring Ken then gave him rather a firm explanation; the RSM realised he was up against someone with similar views to his own and they settled down for a very convivial session.