Diego Maradona is the greatest football player I have ever seen, but as a coach he sits somewhere between a comic opera and a train wreck. Philip Larkin was one of Britain’s finest poets, but to read his music criticism is to wish someone had heaved his typewriter into the nearest river. Ronald Reagan qualified as an A-grade B-movie actor, yet as president – the biggest acting role on the planet – he proved decidedly C-grade. Switching genres can be tough.