Nic Jones on Songs of a Changing World, as it happens.  Certainly not an Irish song, of course, though Marian quotes verses which I've never heard.   Presumably it was the McCalmans who added them, for obscure reasons of their own.  Colin Wilkie's powerful song stands better unadulterated, to my mind.  We've discussed this before, I think; the German mining disaster concerned happened in 1963, apparantly: last time I mentioned this, somebody told us the details.