Hamish Henderson's own account:

"When I heard a verse of D.Day Dodgers to the Lili Marlene tune, I thought: Now this is it, this is the thing, we are going to make a good song of this. I grouped the things together and the song as it is sung today is my song, but it already existed in fragmentary form before I used it. At one time I was accused for being too sentimental in the last verse [...] but I don't think so. I think the juxtaposition of the Lady Astor verse and the verse at the end is powerful." (Hamish Henderson, Folk News No ?, repr. sleevenotes 'A Man's A Man')

The last verse he refers to is the one starting "Look around the mountains ...".

The version Alec Somerville gives above is substantially Hamish's version, apart from verse 5 which is not in any of the three versions I've got. It may still be Hamish's, though. The Lady Astor verse actually seems more tame than the version quoted by Jim Dixon in the first post.