Anything to do with World War II, perhaps? (not implying,
@BanburyBlue, that you are an extremely aged gent

) -- a time when Britain was frantically doing all it could to produce as much of its own food, as possible; sprouts are one of the not hugely numerous crops which do outstandingly well in Britain: so vast numbers were grown and eaten -- perhaps, from necessity a centrepiece of wartime Christmas dinners; since then, become a tradition with a patriotic flavour?
I gather that one of a number of British things which were unfamiliar and "not altogether joyous" to the great number of American servicemen who spent time in this country in World War II: were Brussels sprouts; which in those days anyway, were little-known in a lot of of the USA -- the Yanks over here, tended not to be keen on the little blighters. One of their number -- "overdosed"" on sprouts for lack of an alternative -- was quoted as saying "this has got to be the fartingest war in history".