As Series Four draws to a close, Executive Producer and Head Writer Russell T Davies talks about his involvement with Doctor Who, the show he was part of reviving after a 16-year hiatus in 2005. Answering fans' questions on the BBC News website, he says that once he leaves he will no longer be involved with the show even for an occasional writing stint. He hands the reins over to Steven Moffat in 2010.
"I think Steven's more than his own man. He doesn't need me at all. I won't write for it in the future. I'm done with it. It's time to move on and I'd hate to be just a ghost haunting the corridors that I used to walk.
"And who needs me? Because Steve's brilliant and they've got a thousand million plans. I'll just be old news and it's about time."
He said he would most miss the people he had worked with. "They are genuinely brilliant people, our designers and producers and the crew at BBC Wales. They are fantastic and they're part of the reason I've stayed for so long."
Despite his intial fears of low budget and a non-peaktime slot, he was pleased with the way the BBC treated the show. "I thought there'd be a lot of compromise, I thought we'd be compromised on budget. We could have ended up with no ratings and a Sunday afternoon slot, so absolutely nothing [was compromised] and that really is the honest answer. We got to make everything that I wanted to make.
"I knew what we'd made was good. So I knew I could sleep at night. I knew even if no one watched it, I could sit there and say I had done a great piece of work."
He added: "None of us ever saw this much success coming. I didn't even envisage a spin-off would be possible."
When asked about his favourite line of dialogue, he replied: "I did love Donna, played by Catherine Tate, in a show we did two weeks ago called Turn Left. She said: 'You liar, you told me I was special' to Rose, when she feels her life has been betrayed and lied. I think she delivers that line with such venom - I love that moment."
Asked which villains or creatures he might have brought back if he'd continued with Doctor Who, he said: "I've used a lot of the classics but the Silurians were always very good. They were a race of lizard people who were the original owners of the Earth. I always thought it was a very clever idea that there was a civilisation before us. I'm not bringing them back but they're ripe to be returned one day."