Saving the universe has taken its toll on the Doctor - Peter Capaldi has admitted that the rigours of the role have hurt his knees.
Capaldi, who returns to the role when Doctor Who airs on BBC1 next Saturday, has revealed that he has developed the same "knee complaint" shared by his predecessor Matt Smith which he believes could be down to the physical challenges of playing the iconic role.
"It’s something to do with running down corridors and turning round very quickly to deliver lines,” the actor says.
Capaldi also admits that he doesn’t believe he has yet fully mastered playing the part which he says is one of the greatest acting challenges he has ever faced.
"I don’t feel I’ve nailed it yet – from an acting point of view, I mean,” he told today's Daily Telegraph. “I don’t yet feel that I know how to do this. Quite who the Doctor is remains mysterious to me – which is of course as it should be – but one of the biggest challenges that I’ve found, and am finding, is that you have to sort of be able to spin on a penny.
“You have to be able to go from pantomime to tragedy, from domestic to epic, within a single scene.
“What I wanted to do, I suppose, was remind people of the alien-ness of the Doctor. Doctor Who isn’t a human being, you see. He’s a creature of the cosmos. His social skills aren’t great. He doesn’t care very much if people like or dislike him, because people aren’t his thing, you know?”
However Capaldi admits that he is loving playing the part and is determined to enjoy every minute.
“It might just be my Scottish melancholia, but the very first day I found out I’d got the job, I started to feel sad that one day I would not have it; that there would come a day, in the not too distant future, that I wouldn’t be Doctor Who any more. And that is why I try really hard to get as much out of it as possible.
"Because one day I’ll just be an overweight has-been, trying to get a meeting with Jenna Coleman and being ejected from a Doctor Who Convention in Bolton for being drunk and disorderly. I mean, this is surely my high point, isn’t it?’”
Doctor Who series 9 begins on Saturday 19th September on BBC1 at 7:40pm
Get your tickets to see Peter Capaldi and Steven Moffat LIVE at the Radio Times Festival at Hampton Court in London on Friday 25th September