Steve Green wonders whether this joke, as told so brilliantly by the late, wonderful Sir Clement Fraud, is the funniest of all time.
I think it is the actual Monty Python 'secret weapon' gag, designed to break the trench war deadlock on the Western Front in 1916 to smash the German advance of 1944. So don't listen to it if you're German.
If you think of it while you watch the clip, it kind of works. (Kind of ;) There's a slight issue with my German reference, of course. But what the hell.