Hi and thanks to everyone who responded.    I'm afraid it's definitely not Brother Can You Spare a Dime, or Hatikvah, or La Mantovana.

In reply to the request for more details, I have very little.    It's a tune my wife used to play on mandolin, though she only knows the first ten bars or so.    She picked it up from an Irish folk band back in the 80s and has never known the title.    We have no recording of it, no idea of any lyrics, or even if lyrics exist ...

The best I can say is I'm pretty sure it's Irish.

I sure hope someone can identify it, coz she'd be completely rapt, and I'd get a lot of air miles :)