As far as I remember, both Norma Waterson and Bob Copper learned the song via the writer of it, Oscar Brown Jr. His album, "Sin, Soul....", from the early 1960s, was not a big seller but def a cult favourite and a sign of hipness. Another influential song he wrote (the lyrics, to a Nat Adderley tune), also on the same LP, was "Work Song", that crops up on Bert Jansch's version of Anji.

On one of the other fRoots CDs there's a Bob Copper version of a Sleepy John Estes song - I think it's "Diving Duck Blues" - that he learned from an old blues 78. I wonder, if he'd performed that live frequently enough, if it would have been given the providence of a trad Sussex song :)