I spent an enjoyable evening once in the company of Bob Copper at his social club where we talked about various music that we enjoyed. From this it was obvious that Bob had a liking for jazz and blues and probably an even wider range. He obviously enjoyed singing blues and I recall hearing a recording of him singing and accompanying himself on a Sleepy John Estes number. I can't say that it was a great listening experience.

If my memory isn't playing tricks I believe that MacColl once recorded John Henry.

You quote Peggy above pointing out that she was responsible for the policy for The Singers Club, However it was at The Ballads & Blues Club before the existence of The Singers Club that MacColl introduced it.
As I have mentioned before, I was there.