is the wearing of a hat absolutely mandatory
Yes. As wiggy says, customers like it. Symbol of authority.. we fly to nations where hat wearing for officials is de rigeur! We also wear uniform in the simulator.
No sick notes for that either.
out-dated, pointless nonsense that I can assure you customers belonging to the 21st century don't give a damn about
Use that line in the interview, then you won't have to worry about wearing a BA hat...