Just came across this old thread, and I note that no-one has answered the original question. Singer Paul Snow says he was there at the time and the 'offending' singer was Redd Sullivan, whose proud unregenerate Cockney approach to songs I much loved. He was a resident at the folk club in the basement of the Partisan Coffee Bar along with Martin Windsor and young Long John Baldry. So happens I was just yesterday recalling my favourite verse as sung by Redd in the South African song Sarie Marain [un sure of this spelling].
The verse was
Peeping through the knothole in grandma's wooden leg
Who will put the cat out when I'm gone?
You can ride a knitted bicycle down the High Street
Oh, a boy's best friend is his mother
Ewan