STEPHEN H,yes we have seen that before, the recollection i have of that time is different, in that the knock on effect of the policy had much more influence than Peggy says
.The good side of the knock on effect was that many singes explored in more depth the repertoire of the geographical british isles. the down side was that   in doing so some of us steered away from some very good american songs of social comment.
My recollection of the knock on effects of their policy is a different one.
.Cyril Tawney by contrast went around trying to quietly encourage singers to look at indigineous repertoire rather than trying to impose rules.
finally MacColls attempts at scottish, irish and west country accents are not very good, and for Jim Carroll to criticse the yetties for singing in their own accents is bizarre