I stand corrected! Elijah Wald is a scholar/musician researcher who I have the greatest respect for. His work on Robert Johnson I highly recommend.
One of the books/references I cited was Dave Van Ronk They Mayor of McDougall Street Mr Wald edited that book and wrote the last chapter.
My original hypothesis that Lonnie Donegan was directly influenced by Big Bill and Leadbelly was not correct.
I had some friends who swore Leadbelly toured the UK.
Nevertheless, Lonnie was a major influence and he may be responsible for the original Blues scene in the UK: Alexis Keorner, Cyril Davies, Graham Bone etc. I suppose we could have another thread on that.
My last comment: Billy Bragg: singer/songwriter social activist wrote a wonderful essay about Donegan
http://www.guardian.co.uk/music/2004/jun/21/popandrock