BBC Wales' resurrection of Dr Who was THE success story in British television last year. Here, as he prepares to be unveiled as the new - and 10th - doctor, David Tennant talks to Rob Driscoll about his dream role, and the weight of expectation that comes with it

DAVID Tennant is pretty clear about his first, personal "Wow!" moment in the role of Doctor Who.

"Standing in the cave of the Sycorax warriors, and sword-fighting a seven-feet-tall Sean Gilder as the Sycorax leader in prosthetics and weird contact lenses, and all of those extras standing there....," offers Tennant, almost going misty-eyed at the memories.

"OK, it might have been in a warehouse in Newport, with special effects put in later on, but that was the first moment I thought to myself, 'This is something special.' And those moments keep coming every day.

"Just being in the Tardis, for example. And getting to act opposite Elizabeth Sladen as Sarah-Jane, a veteran Doctor Who sidekick who returns in the next series.

"I used to watch her when I was a kid, eating beans on toast and a cup of Irn Bru. She looks the same and sounds the same!"

It's clear that 34-year-old Tennant is the product of a perfect "Where Did It All Go Right?" generation, a well-behaved Presbyterian minister's son from Paisley who lapped up all the right things on the telly. And now, here he is, playing one of his own all-time heroes. Is it any wonder he keeps pinching himself?

"It's mad, it's crazy - how unreal is this?" he smiles. He knows he's a lucky boy, being given this almighty present, to take possession of the Tardis as the tenth Doctor Who.

It's a double-edged sword, of course, making good what Christopher Eccleston started earlier this year. But already, media and insider reaction to his debut as the world's most famous Time Lord in The Christmas Invasion (on a TV set near you on Christmas Day) would suggest he's got it sorted.

And when his casting was announced, comments posted on the official BBC Doctor Who website were overwhelmingly in favour of the choice.

Yet Tennant himself admits he's always been "preposterously single-minded" about his career.

"I was three years old when I decided I wanted to be an actor," he says. "I just loved watching people on the telly. I was watching stories being told, and thinking 'this is just great.'

"I think I had a conversation with my parents about who those people were in the TV, and as soon as I had an understanding that this was a job, that people got paid for telling stories, that was what I wanted to do."

Fast-forward three decades or so, and Tennant is on the precipice of being a household name. He made us sit up and notice as DI Carlisle in BBC1's Blackpool (which, somewhat ironically, swept the floor with Russell T Davies' Mine All Mine on the other side).

But vengeance was Davies', who nabbed the good-looking, 6'1"-er for the title role of Casanova. And only last week, Tennant was showing another side to his talents, as a psychopathic killer in ITV1's thriller Secret Smile.

Now, he is acutely aware that many viewers will be tuning in to the Doctor Who Christmas special purely to see how he measures up in such an iconic role.

"It's very easy to feel the weight of history pressing down," he said. "Getting over that and getting on with it is part of the trick of the whole gig, really. When you're playing a scene, that's what you focus on, that overrides everything."

As a young lad, Tennant's favourite Doctor Who was Tom Baker. "My first TV memory is being entranced by Jon Pertwee regenerating into Tom Baker," he says.

And Baker himself sent Tennant a good luck message from the set of Monarch of the Glen this summer, when news of his casting as Doctor Who was made public.

"That was another pinch-me moment," smiles Tennant. "And I got another good luck message from Peter Davison, who was filming Distant Shores at the time. I was about ten when Tom regenerated into Peter Davison, so again, another amazing moment. In fact, Peter came on set one day with his children, which was a big thrill both for them and me!"

Tennant recalls that when he was first approached by BBC Wales and Russell T Davies to play the Doctor earlier this year, he merely laughed.

"I found it hilarious and impossible," he says. "And I remember Russell, very perceptively, saying, 'Don't say anything now, because I know the experience is quite a weird one'.

"And it is a weird one. The thing is, I love Doctor Who, I always have. But I never expected to be considered for the part."

The regeneration process of Doctor Who is something Tennant admits is an attractive part of the role.

"The fantastic thing about the regeneration process is that every time the Doctor goes through it, he changes to an extent," he says. "So as an actor, you get to work on a blank canvas where you don't have to worry too much about what has gone before.

"It's interesting, because he's always going to be the moral egalitarian, humanitarian, slightly wild, slightly anarchic bloke that he's always been. But because he's getting older he's moving on. He's seen it all before, every alien creature with a superiority complex."

Tennant reckons that viewers are going to see a slightly more no-nonsense Doctor than the one portrayed by previous incumbent Christopher Eccleston.

"We are more aware that he's someone who fought a war, lost all his people and because he's the last Time Lord, the last authority in the universe, he's less indulgent, more ruthless," he says.

The other striking difference between Tennant and his predecessors is his overall look, which he describes as "Geek Chic." Tennant, along with costume designer Louise Page, wanted a look that was both distinctive and effective, something that clearly states: 'It's The Doctor'.

So they opted for a tailored calf-length coat, chocolate brown, with a blue pinstripe suit and white plimsolls.

"I wanted something that I'd enjoy wearing, an outfit that would look good and feel right," says Tennant. "We also wanted something that was modern, without being specifically en vogue.

"I also wanted an outfit that wasn't too authoritarian. So that's why I opted for a scruffier-styled suit. It's more what you'd expect to see a student sporting than a college professor. And inevitably the look is influenced by the sort of things I like wearing."

However, the audience are going to have to wait a little longer before they see David stepping out in his new outfit, as for part of the Christmas special David will be tucked up in bed and sporting a pair of striped pyjamas!

At the end of the last series, viewers witnessed the start of the regeneration process. The Doctor is still undergoing this process as we enter the Christmas special.

Shortly after returning to the Powell Estate, the Doctor says his hellos to Jackie and Mickey before collapsing into unconsciousness.

With the world under attack from the evil Sycorax, Rose feels powerless as she tries in vain to find a remedy that will get him back on his feet.

"The regeneration process is a severe biological process which takes a fair bit of time," explains Tennant.

"This is not good news for Rose and the rest of the world, because whilst he's going through this, the earth is being invaded by the Sycorax.

"It's a very difficult time for Rose. He hadn't prepared her for the changes he'd undergo. So whilst the Doctor is recuperating, Rose is trying to fathom out how she can save the world. She's also trying to understand how she feels about him now."

So will Rose still want to travel through time and space with this man, now he's got a new face and mannerisms?

"The Christmas episode is a new start for the Doctor and Rose," says Tennant. "They've got to rediscover each other and decipher whether they still feel the same about one another.

"Despite the new face, he is fundamentally the same bloke, he's still the Doctor and still has a huge amount of affection for her.

"However, it's not just the way he looks or the way he talks that is different. The Doctor's outlook on life has changed, as has the way he tackles situations. I think he's just hoping Rose can accept the changes and they can pick up where they left off."

As a Scot who has been living and working in South Wales for the past few months, Tennant stresses that the welcome he's received has been phenomenal.

"I'm having a great time down in Cardiff and Newport," he said. "Wales is a great place to film. You can be in the countryside or by the sea for one scene, and you can be back in the city in no time."

Tennant has already had several experiences of the obsessive Doctor Who fanbase.

"Every Doctor Who fan I've met has been completely charming," he says. "They're always warm, polite, and enthusiastic about the show; they're delightful, welcoming and supportive.

"What's fascinating is the range of people who come up to you as a Doctor Who fan. They're not just a certain type of bloke, but you get women of all ages, young kids, elderly people - they've all come up to me. And that, I think, reflects the genius of Russell T Davies, that he's created a show that attracts a genuine nine-to-90-year-old audience - well, younger than nine, really."