I’ve interviewed Stephen Hawking twice. On both occasions it was in his old office in Silver Street, Cambridge – in front of his huge poster of Marilyn Monroe. The first time, in 1989, I was a little anxious, not because I was with the world’s best-known scientist, but because I found the awkward silences waiting for his answers hard to manage. What do you do, having asked a question, during the two or three minutes it takes him to put together a sentence on his machine? You can’t stare at him for that long – we’re not equipped to do that with anyone for more than seconds. Ignore him? The way we ignore other crippled folk, without realising it? Hardly!