'People really do love the Doctor, they like seeing this mad dude turn up and save the day, using pencils, a lampshade or whatever it may be. This baffled man, quite bafflingly, saving the world.’

'He’s like Robin Hood or Sherlock Holmes, an enduring character in a fairy tale you can just keep reinventing,’

'He is always the cleverest man in the room, but he’s not always certain what’s going on. It is funny seeing clever people look baffled. I thought a lot about Einstein when I was preparing for this. The Doctor should be very clever and brilliantly brave – when the moment calls, he is a leader – but he should also be funny, and a bit ridiculous.’

‘How long is a piece of string? I take it a year at a time. We’ll see how the land lies at the end of that series, and what Steven Moffat is doing. I’m desperate to do a play again when I’ve finished, and maybe try writing one for myself, and I’m very interested in trying to cultivate a film career. But I’ve got a lot of work ahead of me with Doctor Who before I can even really contemplate what comes next.’