Ralph Rinzler sent over by his record company about 1956 ? Too early.

Ralph was certainly in London in 1959 and appearing at the Ballads & Blues regularly. As far as I am aware he hadn't made any recordings at that time. (The Greenbriar Boys recordings came later) I believe he was doing what many Americans were doing at that time, leaving university and doing the European trip similarly to Peggy Seeger. In fact when Peggy's visitor's visa ran out and she had to leave the country temporarily it was Ralph that took over her guitar and banjo lessons. It is my understanding that Ralph was not a poor man and if was staying at a decent hotel at that time then it certainly wasn't by earning any money on the folk circuit.
I don't believe that Ralph returned to the UK after his brief stay here until he brought Doc Watson over in the sixties.

Undoubtedly some so called folk performers have come over on promotional tours but at that time I can't at present think of any.
Possibly Vanguard chipped in something when Ralph and Doc did their visit but apart from that ?

Ralph was certainly someone to whom lovers of American "folk" music owe a great debt.

Hoot