"Is Brian Mullen a 'source' singer'"
No, he isn't, though he is a very nice feller!!
For the record - I was talking about source singers; there is a version taken down from 'an Irishman in Liverpool' in 1906 and included in The Journal of the Folk Song Society by Frank Kidson.
My information that Mrs Cecelia Costello sang it was in fact incorrect - she didn't; I was confusing it with her 'The Cruel Mother'.
Jim Carroll