At last a real Nephews thread in true Uncle Roger style and worthy of some serious PPrunery.
I think we've comprehensively shown where the letters come from (interesting that few have clung to the 'B' annotation but rather more to the 'F' and 'AC') and of course this was common practise when Beagle were a lad between the wars. The best excuse I've seen for sticking to a particular format is whatever was on the Squadron Crest as drawn by Chester Herald and approved by the Monarch of the day - If CXI(Fighter) was good enough for the King who am I to change it?
I also note fashions have changed - all the WWII old boys at my reunions spoke of two-nine while all from the jet age on talk of twenty-nine.