That guy Ivan mentioned above by mja was one of Paul's boyhood friends. Paul in that Charlie Rose interview talked about Ivan and how he went on to become a Greek & Latin professor at Cambridge, then died tragically young of Parkinson's. On that show, Paul read a poem he wrote in memory of him, called simply "Ivan".
I never knew about Ivan before. That would make four dearly loved people Paul has lost in his life -- all untimely and tragic -- Ivan, John, Linda, and George.