To my knowledge the song was written by Jim McLean, not sure when (late 60s??), he also wrote several other songs recorded by Alastair McDonald on an album called "Scottish Battle Songs" which Jim produced. My own favourite of his was a song called "Where is the Glasgow?" which was written in response to a song of the same name by Adam McNaughtan which Jim McLean considered over-romantic. That song is on an album called Gallus Glasgow Songs and sung on it by Iain Mackintosh. Jim Mclean today is not around the Scottish folk scene and works (I think) in electronics.