"Guest" above is correct - composed by accordion player Seamus Shannon. The best piece of whistle playing I ever heard was Finbar Furey playing this at a Thurso Folk Festival, 1978, I would think. I do still have the recording.
Someone posted a version on "thesession.org" - I'd need to check the accuracy of the transcription, which can be a bit "hit-or-miss", but here it is, anyway :
It's listed as on 11 recordings there - I certainly have heard it played by Seamus Creagh on fiddle [ you can get it on "iTunes", I think ] - Mick Mulvey on flute, and also Raymond Roland as part of Le Cheile", on accordion. A wonderful piece of music.