The words of the Field of Athenry are clearly just a variant on the 1888 version - I'd say it's a good variant, with changes for the better, but the changes are pretty minor. I can't see that Pete St John could call it an original song on the basis of them alone. M

On the other hand it is quite possible that the tune might have been made up by Pete St John, which would give him more of a claim of its being his song.

I think the case for "Will you go lassy go" and the McPeake's is stronger. From what I have seen, the development and change from the "The Braes of Balquidder" or the "Highlands of Heaven" (both on the DT) is a lot greater than it is for the text of Athenry. Of course there might be some intermediate version that I haven't come across.