Wil Marlow bids a sad farewell for now to the latest incarnation of Doctor Who...

So begins the end of the current run of Doctor Who, and what a ride it's been.

There's been thrills in the form of Big Ben being destroyed and the (almost) triumphant return of the last Dalek. There's been plenty of scares from walking mannequins, gas mask-wearing bomb victims and, not least of all, that cold, calculated Dalek.

Perhaps most surprisingly of all there's been plenty of heart strings tugged. The intense relationship between the Doctor and his companion Rose Tyler has brought many moving moments, as has Rose's touching relationship with her family, particularly in the episode where she went back in time to try and save her father's life.

The emotional dimension of Doctor Who - even the plight of the last Dalek managed to move viewers - is mostly down to one man, the show's writer and executive producer Russell T Davies.

"Well, that's what I write," he says with a laugh. "That's what you're getting when you employ me, quite frankly. Otherwise you might as well ask someone else."

When it was announced last year that the 42-year-old, already well-known for writing well-respected dramas such as Queer As Folk and The Second Coming, had been given the task of resurrecting the dead Doctor, Who fans rejoiced.

Not only would it be back after a 16-year hiatus, it would be back under the guidance of a hugely talented writer and a self-confessed Doctor Who fan.

For Russell himself, however, it was nerve-racking. So much could have gone wrong.

"Science fiction at prime time didn't exist any more," he says. "A lot of friends and colleagues were telling me it was a niche programme, and that Saturday drama was dead.

"There were a lot of factors pitted against us, all of which I believed, I have to say. I was sitting there going, 'Oh my God, what are we doing?'," he laughs. "It was scary. But that made the end result beautiful."

He is speaking the day after he and his team have put the finishing touches to the final episode of the series, and, boy, is he proud of it.

"It's like the male and female versions of the programme put together," he enthuses. "There's a lot of action and a lot of emotion as well. And that's when action gets it right - when you really care about the people firing the laser beams.

"It is everything I wanted it to be - the music is brilliant, the effects are brilliant. A lot of series don't reach a climax - I thought the last episode of Desperate Housewives was quite relaxed in the knowledge it was coming back - and I think that's a mistake.

"You want to leave people punching the air and I think we've pulled that off."

Rumours of a big twist where the Doctor is revealed to have been under Truman Show-style observation for the entire series are apparently unfounded.

"Oh rubbish," laughs Russell. "I don't want to give away any plot, but as if! There's nothing more disappointing in the history of fiction than The Wizard Of Oz when Dorothy wakes up and it's all been a dream. I would never do that."

The writer has had no time for reflecting on the success of the series. As was announced early into its run, the BBC asked for another series for next year. Pre-production has already started and Russell has some of the scripts in front of him as he talks.

"We just have to get on with it," he says. "And because we've got a new Doctor coming up it makes us worried all over again. But I think it's very healthy in that we don't rest on our laurels. There hasn't actually been a moment of, 'Hooray, it's a success!' because now it has to be a success again next year. It's still as scary as it ever was."

When Christopher Eccleston, who plays The Doctor, announced his departure earlier this year after just one series it came as a shock to fans and viewers. But Russell says it wasn't such a shock to those working on the programme.

"These things are always reported as though he walked into the office one day and said, 'I'm going'," he laughs. "We worked together for nine months, and we were talking all the time. When you see the final episode, and the Christmas special after that, you'll see it's all absolutely planned."

And now Billie Piper, who plays Rose, is reported to have decided she's leaving mid-way through the next series. Russell again says that's not the case, but is unwilling to say what the real story is for fear of ruining future plotlines.

Instead we're just going to have to wait and see whether it will be Chris or his replacement David Tennant (who played Casanova in Russell's recent drama of the same name) who will be The Doctor in the planned 60-minute Christmas special, and how long Rose will continue to be his companion.

"Having changes in the cast so early on is always a worry. But at the same time it's one of the things that keeps us on our toes. Just by casting David we're not becoming complacent because it's his face on screen and we've got to make it every bit as good, if not better, for his sake."

Russell is giving nothing away about what will happen in the Christmas special, although he does reveal that there will be a regeneration sequence in which ninth Doctor Chris becomes tenth Doctor David. And it sounds like David will have his hands full in the second series.

"We're going to see some alien planets next time round," says Russell. "I've been cautious about that in the first series because we want to get it right. It's one of those science fiction things that can go horribly wrong if it doesn't actually look like an alien planet. But I'm very confident we can do that now.

"And the Cybermen are going to come back. Hooray! We like them. After the Daleks it was inevitable really. The old elements work very nicely. There's a bit of nostalgia and they appeal to the new viewers as well. But there will be plenty of new stuff as well."

The Daleks, however, will not be back.

"Oh no, we've done them," Russell says. "Because of what happens in the last episode, I'm not sure we can take the Daleks anywhere else after that."

* Doctor Who: Bad Wolf is on BBC One on Saturday June 11, followed by the final episode Doctor Who: The Parting Of The Ways on Saturday June 18