Lady Nancy, I think you will find that it was horse racing on an island in the middle of the river, long since dredged away by Lord Armstrong to make it easier to navigate coal down the river. There was indeed a pub on the island. A bridge was erected using boats to get the horses across. On the occasion of the song it had rained so hard that the horses could not be taken across hence the call about the cuddy (horse/s) being stolen? Coffee Johnny was the blacksmith responsible for shoeing the horses and was a very tall man who was frequently goaded into a fight.