A writer can bemoved by someone's experience and fit the words around .It could have been a fusion of thousands of people and their experience. I wrote a song about my Grandma but changed dates and places , she became a symbol of her times. Ian Campell knew Bob well and what he stood for so it's possible. Unless we get it from the horse's mouth I don't know. he never claimed it was about him.. That was what Ewan McLennan said and he's a young chap.