Doctor Who returns to our screens this Christmas for a one-off special, starring David Tennant as the tenth Doctor and Billie Piper as Rose Tyler.

In this special episode, the Doctor and Rose return to Cardiff where the Doctor languishes in bed, recovering from the draining regeneration process, while Rose and Mickey battle sinister masked Santas, a killer Christmas tree and a plot to take over the world by the Sycorax, a monstrous alien race.

David Tennant steps into his role as the tenth Time Lord in Doctor Who – The Christmas Invasion

It's been a fantastic whirlwind of a year for David Tennant. Over the past twelve months, he has rocketed from being a relative unknown in the eyes of the public to a household name.

However, David first graced our screens in the 1994 drama Takin' Over The Asylum. It was roles such as Reverend Gibson in Andrew Davies' adaptation of Trollope's He Knew He Was Right, the maverick DI Carlisle in Pete Bowker's acclaimed Blackpool, and then the legendary Casanova in Russell T Davies' beautiful, fast-paced and ground-breaking serial that have made him one of the the nation's favourites.

However, it's his role as the tenth Time Lord that is set to cement his place in history.

When Christopher Eccleston returned as the ninth Doctor last year, sixteen years had passed since the series had last aired and noone could have predicted its phenomenal success.

Now mid-way through filming, David has settled into his role and is enjoying the experience immensely.

David explains: "It was funny, when I first got asked I just laughed! I found it hilarious and impossible! And I remember Russell, very perceptively, saying: 'Don't say anything now, because I know the experience is quite a weird one.'

"But it's such a great job! I mean, I get to play a Time Lord and have a TARDIS: you can't knock that!"

Fans have already had their first taste of David as the tenth Time Lord. Eight million viewers tuned in to witness the climatic scene of Bad Wolf/Parting of the Ways where Christopher's ninth Doctor morphed into David as the tenth.

The regeneration process is something David 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. 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."

David continues: "Viewers are going to see a slightly more no-nonsense Doctor and that is influenced by what Chris did with him. 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."

The other striking difference between David and his predecessors is his overall look. David, 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. The look - which David himself labelled 'Geek Chic' - has been a huge hit with fans and critics alike.

There have been a host of articles written about his look, much to David's amusement, including a 'How to dress like the Doctor' in monthly sci-fi magazine SFX.

"I wanted something that I'd enjoy wearing, an outfit that would look good and feel right. We also wanted something that was modern, without being specifically en vogue. I wasn't trying to create a Times Style article about it, but I'm glad people like it so much," David laughs.

"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. 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."

He continues: "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. 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."

David has been a lifelong fan of Doctor Who. His favourite Doctor is Tom Baker and he admits that watching his hero in action had a part to play in his decision to be become an actor.

Like viewers today, he tuned in on a weekly basis to catch the next exciting and scary instalment. The fear factor is something David feels is a key part of the series and an important part of growing up.

"Being scared and having nightmares is part of our childhood. The Christmas episode does have some scary moments. Sinister Santas, a spinning killer Christmas tree and of course the Sycorax. But that's great. I don't think we should shy away from it. Kids love fear."

One of the biggest surprises of last year was the varied age range of the audience Doctor Who attracted. The series really hit a chord with viewers of all ages and has been heralded as good family entertainment.

The majority of David's television and theatre roles have been for a predominantly adult audience, so how does he feel about his new army of younger fans?

"It's genuinely watched by everyone, aged seven to seventy, including groups you wouldn't particularly expect to be huge Doctor Who fans.

"I'm continually surprised by the number of trendy teenage girls and middle-aged mums who come up to talk to me and who genuinely love the show. I think that's what's extraordinary and unique about it.

"But that's how it should be. I think it's a good enough show to justify that kind of cross-spread of audience. I doubt I'll ever do something that attracts such a varied audience again."

Aside from David's eclectic array of television credits, he has an equally impressive number of theatre roles to his name. Two of his most recent roles were for the dark and gritty plays, The Pillowman and Look Back In Anger.

For the latter, David was awarded the Best Male Performance award at the 2005 Critics Awards for Theatre of Scotland for his performance as Jimmy Porter.

His younger audience are also about to get a taste of him in action as Barty Crouch Junior in the fourth Harry Potter film, The Goblet of Fire.

Prior to the Christmas episode of Doctor Who, David will be appearing in ITV1's dramatisation of Nicci French's novel, Secret Smile.