I was taken there a few times as a child & visited once or twice as an adult too. My recollection is of the childhood visits that both Ewan & Bert Lloyd were pretty scary, and that you would need to be a pretty good musician to offer to perform at all. The problem with the proscription was that many of us grew up in cities where the folk tradition had been gone for a century. The number of songs originating from the London boroughs of Camden & Haringey are small and there are only so many times you can sing The Bailiff's Daughter of Islington. In my mind the proscription is linked with the Anti American feelings that a lot of adults on the Left had at the height of the Cold War. If you think they were harsh on American songs you should have heard people from those political circles on chewing-gum and what were then known as blue-jeans.