Paddy's Sick Note / Pile of Bricks (Pat Cooksey of this parish)

and pre-dating that - Even listening to Gerrard Hoffnung do the story I can't help laughing even though I know most of the gist. And I have seen references to earlier stories of that ilk. But Mr Hoffnung (Debate at the Oxford Union LP (CD etc)) has a delivery that just - well - timing is everything.