It’s late December 1982 or thereabouts, and I’m standing in a Suffolk church before hundreds of people, wearing a cassock and surplice, with a churning stomach. This year, at my prep school carol service, it’s my turn to sing the opening solo to ‘Once in Royal David’s City’. The trouble is, the solo is sung acapella – the organ will give you the opening note, but if you go a semi-tone off-kilter halfway through before the full choir come in with ‘He came down to earth from heaven’, there’ll be the most awful discordant balls-up and everyone will know.