Not found very often in tradition (see listing in Roud), but it became popular in the revival; during the '60s, I'd guess. Probably the texts 'Dead Horse' and 'stormalong' posted are of that vintage; they look to be expansions of the Haxey set.

It seems most likely that the occasional appearance of Churchill and the Germans in this song is due to its persistence in tradition throughout the 20th century rather than evidence of an 18th century origin; that at least is the opinion of editors such as Patrick O'Shaughnessey and Frank Purslow, and I see no reason to dissent. Actually, that's only in in the Haxey version anyway; though it appears that by the 1970s the Boggins had dropped him and restored Lord Roberts. I don't know what they sing nowadays, but could probably find out; mind you, if Will Noble and John Cocking got their text directly from them, it will have been relatively recently, so perhaps Churchill is back in favour again.