The term ‘rock star’ remains pretty elusive within the world of rock ‘n’ roll. It’s pretty impossible to define, to be fair, but it’s a bit like one of those strange terms where, while it might be difficult to officially put into words, you know what rock ‘n’ roll is when you see it. I remember a friend within the music business once telling me about a time when he was backstage at Glastonbury, hanging out with artists and swept up in a mass of…