Following discussions on Jon Boden's Folk Song a Day and threads on Mudcat songs about the Spanish Civil War, I did a bit of poking about. Here's Adam Faith's jaunty waltz-time 1962 version arranged by John Barry.

http://www.youtube.com/watch?v=VX0-QP8We8c

Jackie DeShannon did a version, similar tune, with different words. !963 single and on LP In the Wind 1965. Trevor Peacock is credited with her words and music. The tune has echoes of Scarborough Fair

There is a suggestion that the original poem was written by J Hooker Hamersley a New York lawyer, investor and poet (died 1901) If so it's not from a translation of a Spanish Civil War song by a doomed Republican soldier. He was a very rich US Republican who was a friend of Vanderbilt, JP Morgan, etc! He wrote a book Seven Voices in 1898

The song seems to have got into Jon Boden and Fay Hield's repertoire via the Forest Camps songbook (I'd guess via Adam Faith's version)

There is a comment on another website that a Sheila Lewis set the poem to music.

I'm not having much luck with Google.

As Fay's album will soon be out it might be nice to find out some more about this moving song.