Watch Douglas Adams tell The Greatest Story Ever Told
The stranger on the train, the biscuits, the Englishness of it all...

The web has rightly been going crazy for the text of an anecdote by Hithchiker's guide author Douglas Adams. Here he is telling the story live on the David Letterman show in 1985. (Skip to 2 min 50 sesconds. H/T John Rentoul)