I was told two years ago that the man who wrote it was then working as a DJ on Mid West radio . At the age of ninety! My father said Dominic Behan didn't write it "couldn't have" - although he would have fixed it up.
It's based on the Jackets Green of course- "down the glen came Sarsfield's men"
https://www.youtube.com/watch?v=rnFY-nGgVg4