Dick is right - it didn't matter how hard MacColl insisted on his authorship, this is a genre where there are strong incentives (like not paying royalties) to think of in-copyright songs as trad. Hamish Henderson saw this coming and welcomed it, for his own work anyway.

I can remember a dinner party that Ewan and Peggy were at where Ewan was telling us a story of how surprised and pleased he was to be told that Shoals of Herring had been collected from a Irish traveller and by which time it had become Shores of Erin

I can also remember being in a pub in Ennistymon in the late 1980s at a time when the road to the north of the town had many trailers on the verges - and I am assuming that it was a traveller who sang a song in that pub that was just about recognisable as Eric Bogle's No Man's Land. Both the words and the tune had been subject to change and the grave was no longer that of Willie McBride.