Well, if the Irish Rovers All Hung Up album says "adapted by Will Millar, then I guess Millar is not the songwriter. Sure sounds like a 20th century composition, not something traditional.
HHere's another link with information about Will Millar:
Guest - you ask where the Mudcat Cafe is. I guess you could say it's a "virtual" tavern that lives on the Internet; but Mudcat Central is where the servers are, in State College, Pennsylvania.