I agree with Steve that this type of song was often made up from floating verses.
My first experience ever of interviewing anybody was in 1969, when I was asked to help a friend record the reminiscences of his grandfather, a Liverpool docker who had lied about his age shortly after leaving school and, not being able to find work, had joined up to fight in W.W.1 - he spent the next few years hauling his concertina across the mud of Europe until he was finally shipped back home, wounded.
It was one of the most memorable couple of days have ever spent.
He sang us bits of this song, which he, unaccountably, called 'The Siege of Liverpool'!!!
Jim Carroll