There was an interview with Mr. Gordon when he appeared at a festival a few years before his death (I think the transcript was published in an issue of the World of DS zine) when he remembered lying in Barnabas' coffin and having to listen to an argument between Dennis Patrick and John Karlen (as the characters of Willie and Jason) before he made his big move.
I think he played "Hand of Barnabas" in a number of episodes.
cheers, G.