Here is the story as to how Christy Moore got the song
I was playing in Derry and staying with The Barrett Family. After my gig we were gathered in Chamberlain St having a banter and drinking tea when a bit of singing broke out. A lad, just home from The Blocks, sang these verses and subsequently wrote out the words for me. At the time the name Bobby Sands was not known to the world as it is today. The following night I played in Bellaghy where the same process took place when I stayed with Scullion. Later on he "sang" McIlhatton for me and told me it had been written by Bobby Sands with whom he had shared a cell while "On the Blanket". The name was becoming known to me.
He used the air of The Wreck of the Edmund Fitzgerald from Gordon Lightfoot, an air which I suspect has earlier origins. My version of Bobby's song is shorter than the original