"Where did you find this one, Jim, and what sort of vintage is it?"
I heard it sung at a club by MacColl years ago
He said he was pointed out to him by a researcher friend who got it from a 19th century broadside - it might have been Bob Thomson, who was doing extensive work on the Madden Collection in the late 1960 and was a great friend of Ewan's.
It was just after that time I heard him sing it.
There's no guarantee that MacColl didn't tinker with it to make it singable, in fact he most certainly did.
As a singer, he was strongly in favour of the practice, though he usually hung on to copies of the original.   
Jim Carroll