A Dave van Ronk CD came out last year, a collection of "rarities" from 1957 to 1969, called The Mayor of MacDougal Street. On one of the tracks he tells the story of being at an English folk club and learning that he was only supposed to sing songs coming out of his own tradition (or words to that effect). He has some harsh words for the organizer of the club - he never names him, so maybe it wasn't MacColl - and decides that the only songs that are really in his tradition are the ones he learned on the street as a kid, so he sings Shaving Cream (lyrics here).