The major is always shown with a beard. British army officers ( unlike naval officers) were not permitted to have beards while in uniform. Covert operatives often had beards while under over, in some assignment, but not in London, in uniform. Applies to all episodes. See more
I've decided I'd like to read from one of my father's books. "Few people realise what our country owes to the gallant men of the silent service. To them, fame and glory seldom comes, riches never. Often they die quiet, even shameful, deaths. Theirs is the ideal patriotism that is prepared to sacrifice home... family... everything... for the sake of the land that gave them birth." Thank you, Dad. And rest in peace.