Any actor worth his salt has a responsibility to reinvent himself from part to part.

We didn't start Theocracy because we wanted to be cool like so-and-so and make money. Our songs aren't trendy, and our lyrics hopefully make people think about certain concepts in a new way.

At university I had a big coloured scarf and people would often say, 'All right, Doctor Who?' And, I thought, I rather liked that notion.

It's been four years. It's been the best four years. It's been wonderful, it's been a privilege to work under Steven Moffat. But I think when you gotta go, you gotta go It's sad, I'm going to miss it. I'm going to miss Comic-Con as well. It wasn't an easy decision, but I dunno, you can't play it forever. And, look, they'll get someone amazing and brilliant, and that's the great thing about the show. It continues, and it will get bigger and better. And you'll forget about me.

As an actor, you'll have ten parts in 2015 - eight of them will go to the other actors above you and two of them you might be close to, and you try to make them as good as you can.

I always go back and do theater. I love it. It keeps an actor improving in a way, it sort of keeps your craft alive, if that makes sense.

There are great disciplines from being a sportsman that you can transfer into being an artist. The preparation, the sacrifice, the constant desire to improve.