Clement Freud's funniest joke

The Telegraph celebrates the recently departed Clement Freud (writer, grandson of Sigmund, chef, politician, broadcaster) with this clip of the delightful old codger telling "the funniest joke ever told." I laughed aloud -- and I loved his Grimble kids' books, which were weird, subversive and funny in just this way.

Did Clement Freud tell the funniest joke ever told?