When did you first know you'd be a writer?
Well I've always loved to tell stories, and my first real exposure to the pleasure of doing that came in high school. I would draw comics - little three page things - on weekends and they'd basically be passed around this school of 2,000 people every Monday.

You could say I was "pushing" stories instead of drugs, and having this huge readership actually taught me to develop coherent storylines, complete with cliffhangers and twists and all the rest of it. It sounds absurd, as I was just a kid drawing comics for other kids, but it really did help me as a budding writer.

How did you rise in the ranks of telly?
Well I went to Oxford University, which obviously helped to open doors in the media world, and I actually wound presenting the old kids' show Play School in 1987. But my real desire was to work on the production side of things, and I became a director and producer of shows like Why Don't You - where I discovered and cast a certain 12-year-old boy by the name of Ant McPartlin. Wonderful to see how successful he's become.

Children's telly was a great training ground for me - even if it was just writing for ChuckleVision, which I did! It helped hone my skills and prepare for adult programmes like Queer as Folk.

How did you tackle the all-important question of casting Doctor Who?
Well in the years between the 1990s McGann movie and our series, just about every actor in the world had been touted as the next Doctor by the media. It was becoming rather absurd, with every possible name - no matter how ridiculous - being hyped. Even celebrity chefs and stand-up comics were all seen as viable Doctors.

I actually had Chris Eccleston in the very back of my mind as we had worked together before, but never really thought such a serious actor would play a seemingly frivolous sci-fi role. So I was as shocked - and delighted - as anyone when he actually put himself forward for the part.

I needed a little more convincing with Billie Piper. At the time she was relatively untested as an actress and I kind of thought it would be as silly as casting someone like Britney Spears. But of course I saw her audition and she was absolutely brilliant.

Eccleston's Doctor is the only one whose origins are never revealed. Were you in two minds about whether you should show or discuss the regeneration that created him?
Well regeneration is obviously a big part of the Doctor Who mythos, but at the same time it only has resonance if the audience has come to know and love whichever incarnation of the Doctor is about to regenerate. We were bringing the show to a whole new audience with Eccleston, so I felt it would be both confusing and just pointless to show his regeneration.

Obviously it was another matter with David Tennant, and we thought long and hard about how to make the regeneration pack a punch. I didn't want one Doctor to just morph into another and everything carry on as normal. I wanted to show how difficult and jarring the whole process is, which is why the Tenth Doctor - Tennant's incarnation - is basically out of action and a bit woozy for much of his first story.

What's the trickiest aspect of making Doctor Who for you personally?
Well the logistics can be a bit tricky as I live up in Manchester and the programme is obviously made in South Wales, so there's a lot of legwork there. On the other hand, making Doctor Who has been a dream come true for me, and I love being able to deal with such outlandish, other-worldly themes. It'll be rather strange to go back to domestic, "real life" dramas.