I met John many years ago, and even visited him and his then wife, who may have been called Lisa, but not sure. They lived right at the top of a tall terraced house in (I think) Crouch Hill, There were guitars and all sorts of instruments, hanging on the wall, all the way up the last flight of stairs. From what I remember of the flat, it looks like that piece was filmed there. He did a TV series, called Hold Down a Chord, in the 60's