I know it's really square but I'm one of those people who piles on the factor 50 as soon as I'm outside.

I was very much into science when I was young - I wanted to be a marine biologist, then I wanted to be a doctor, and then something else, I was always changing.

I went to University after my A levels and did a degree in performing arts. It was only when I got there that I realized there were stage schools out there, and you had your union and your contacts and The Spotlight and this whole world of the acting industry that I had no idea about. So when I graduated, I took a year out and just thought really hard about whether it was something I knew enough about, and whether it was the career I could dedicate the rest of my wacky life to.

David Tennant is a massive fan, and grew up dreaming he would be the Doctor Who one day. So I did feel, when I first got the job, "Right, now I've got to do loads of research into absolutely everything Doctor Who." But that's not possible to do in a short space of time. So my knowledge has been growing and developing as I've been doing it, and that's been fine. That's been appreciated by the fans, and the executives never expect me to be brushed up on absolutely everything.

My own style is one of not much effort.

I went to a very academic school that actually - when I got to the point of wanting to pursue acting, they just had no idea how to do that, because all of their contacts were very academic.

Whether people watch Doctor Who or not over here, everybody knows about it. It's a British icon, it's so part of the nation.