IF YOU WEREN’T there, you might find it hard to imagine the extraordinary impact The Hitchhiker’s Guide to the Galaxy made when it was first broadcast in 1978. After all, it was only a sitcom – a science-fiction sitcom even – and it was on radio to boot. At the time Radio 4 wasn’t so much fuddy-duddy as the preferred listening of the living dead, and only people applying for jobs in radio comedy ever tuned in to its sitcoms. Hitchhiker, though, was different. Sonically adventurous, strikingly imaginative and, of course, very funny, it rode the wave of science-fiction madness generated by Star Wars, and swiftly begat spin-off novels, a TV series and endless rumours of a feature film which continue to this day. It also made its writer, Douglas Adams, rich and famous at the age of twenty-seven. In some ways, it seems, he never quite recovered.