So there are various theories as to the origin of the version that the Clancies sang. It ISN'T the tune that Sam Larner sang - that is quite distinct. Did Louis Killen learn it from an Australian source - anecdotal evidence says he did, but anecdotal evidence also has Sharp collecting in Norfolk, which he didn't.
So far as I am concerned, the jury is still out on this one, unless someone can provide some more precise information.