What are the mil rules for headwear in churches also?
Well, whilst Zulu Mike is absolutely correct, they were even more simple as understood by the Chief Petty Officer Gunnery Instructor marching a contingent of sailors into Rochester Cathedral for a Church Parade. As each file entered the cathedral, they were expected to smartly remove their cap in the time-honoured naval manner, and all did so except one, at which point the Chief GI bawled out at the top of his voice, "Take your 'at off in the 'ouse of Gawd, c**t!"
Jack