The commonest version you hear in the British Isles these days is due to Hamish Imlach, who was trying to remember the John Jacob Niles tune at the time, got it horribly garbled, and decided to stick with it.

I've more than once heard Irish singers insist that the Imlach version is an Irish tune. As far as I'm concerned it sucks and they're welcome to it. I just wish people here would drop it and do the Niles one instead.