After four years in the Tardis, David Tennant finally leaves Doctor Who after a spectacular two-part adventure to be shown on BBC1 over Christmas and the New Year. Here he tells What’s On TV what to expect – how the Time Lord battles the Master, meets Donna Noble again, and regenerates into Matt Smith…

What can you tell us about your final two-part adventure called The End of Time?
“Well it’s my finale and it definitely won’t disappoint. It’s just huge and the cliffhanger between the two episodes amazingly keeps going on and on. It’s brilliant in its scope because you keep thinking, that’s the cliffhanger and then something else happens, then something else and you think well that’s it it’s finished – and then something brilliant you never see coming happens. It’s great to have some returning stars back too. John Simm is The Master, Catherine Tate is Donna again, and Bernard Cribbens is her grandfather Wilf.”

Is Donna quite central to the story?
“Well Donna was last seen at the end of series four when she was made not to remember any of her adventures with the Doctor. We were told all hell would break loose if she did remember. So when the Doctor bumps into her grandfather Wilf again it’s clearly imperative that they don’t bump into Donna, or that Donna isn’t aware of what’s going on. I think it’s fair to say that Russell T Davies wouldn’t write that into a script unless it’s seen through. You can probably imagine the chaos that’s going to happen there.”

There are some Ood as well, aren’t there?
“Yep you see one at end of Waters Of Mars. In this we get to visit the Oodsphere again where the Doctor’s told ‘Your song will be ending soon’. The Ood are actually calling time on the Doctor and for him that’s where the story begins. But we find out that he hasn’t gone straight there and he’s running and trying to pretend his incarnation isn’t doomed. But the Ood tell him he should have got there sooner because time is moving against him and the rest of creation in the shape of The Master who has miraculously been brought back to life. The story iunravels from there pretty much.”

So do you meet the Master early on?
“Not too early on as there’s a bit of hide-and-seek going on between the Doctor and The Master. Unlike the last time you saw The Master when he was the Prime Minister Harold Saxon, he’s in a slightly more feral state this time. He’s hiding not only from the Doctor but from humanity at large. And the process of bringing him back to life hasn’t left him the healthiest creature in the world. There’s also a desperateness to him this time. He wasn’t the most sane of characters at the best of times but John Simm is just sensational – he kind of just eats the screen up with a feverish intensity, it’s extraordinary. And the Doctor knows he’s dying so needs to find the Master. The Doctor’s relationship with The Master is confusing because he knows he has to sort of shut him down. At the same time he wants to reach out to him because he’s the only vestige of the Time Lord’s people that’s left. There’s that kind of Bond there.”

What are the exchanges like between you and The Master?
“There’s lots of dialogue between them, and John Simm’s brilliant. John really enjoys the part as well. He gets to go barking mad which he did the last time and you thought that was as bad as it got, but this time he’s off the scale! He also gets to blow things up which he enjoyed. There are a lot of fireballs going off at various points. When things start to explode behind you it’s tricky to look cool. Everyone’s trying to crank it up for the finale and make everything that little bit bigger than before. I remember the heat on the back of my head was incredible at one point. But then you look back and realise how cool it looks when you see the scene!”

The Doctor spends a lot of time with Wilf doesn’t he?
“You get these incredible scenes with these two old men – Wilf who’s 80 and the Doctor who’s 906 or so and it’s incredibly moving to see these old boys talking about life and death. He’s as much the Doctor’s companion in this as anyone is. He gets on board the Tardis and has a trip with the Doctor, which is fantastic because Bernard Cribbens last did that in 1966 with Peter Cushing in the movie. Daleks: Invasion Earth 2150AD.”

Are these dark, scary episodes?
“It’s got a different scale to it. It’s kind of like a fable, with fairytale elements. It starts with this narration from Timothy Dalton in this booming voice. He says something like: ‘In the last days of the human race everyone was having bad dreams’ and it’s got that kind of epic scale to it and every ten minutes or so Timothy comes in with a bit more spooky narration. There’s a huge long sequence where nobody says anything and the Doctor and the Master are simply trying to find each other. It’s different from anything we’ve done before. Russell’s so clever and knows exactly how you can kind of tease these things out and just when you think it’s getting a little bleak he sprinkles in a little bit of comedy. It’s a beautifully constructed story.”

What’s June Whitfield’s role in the story?
“She plays Minnie the menace, who had an incident in a police box once – not the Tardis another police box – and she likes to remember that when the Tardis comes along. She’s one of Wilf’s pals and she’s in it right throughout actually.”

Are John Barrowman and Billie Piper back as Captain Jack and Rose?
“They’re not in the Christmas episode. New Year? – you’ll have to wait and see…”

We’ve heard there are some weddings, is that right?
“Yep Donna’s getting married. In fact that’s when The Doctor meets Donna again, he also meets her husband-to-be and they’re all set to get married. But clearly that’s not going to work out. Well certainly not as smoothly as she might anticipate.”

Was it strange being in the Tardis for the last time?
“That actually came in the Sarah Jane Adventures which I filmed after. In a way that was a nice decompression week which I think was probably for the best. I think if my last day had been my last Doctor Who scene I’d have been a wreck, so as it was I was spared all that.”

Is the Doctor obviously heading towards regeneration throughout this?
“Well I think he knows he is in trouble from the end of The Waters Of Mars. He realises he went too far there and the universe is catching up with him and the Ood have come to call him to his fate. He says quite early on in the Christmas Day episode ‘I’m going to die’. He knows it’s coming, he feels it coming and there’s something broken about him. At the beginning of the story you see him trying to cope with that knowledge in a bizarre fashion like wearing a silly hat and talking nine to the dozen to the Ood trying to make it all OK. But he knows he’s running from the inevitable. These episodes seem bigger and scarier and the whole scale of it is kind of imposing, because it feels like there’s a drive towards his end that is inescapable for everyone involved.”

Do you run about a lot in this adventure?
“There’s not as much running as normal which is fair enough because Bernard Cribbens is 80, and we wouldn’t want to kill him off. Although saying that, he’s pretty good, he did keep up. He’d never give up he was so fearless. I’m strapped down for one sequence so had to be wheeled about. There were lots of big stunts and lots of things blown up behind, and a bit of wire work, too. I don’t think I got body-doubled in this. I was allowed to do everything.”

Why did you pick now as the time to leave Doctor Who?
“It was less about fear of being typecast, than if I stayed I’d never have the guts to leave because I love it so much. It would have been very easy just to keep going. It’s felt a very special and unique time, not just a job. I’d hate it to become just that. So this felt like the brave thing to do. If I’d stayed much longer you’d have never got rid of me.”

Did you give any advice to Matt Smith about taking over from you as the Doctor?
“I haven’t given him any advice. What would you say really? It would be patronising and inappropriate. We’ve chatted of course and he’s got such enthusiasm and focus for it. But I wouldn’t presume to tell him what to do. I’m quite jealous in that I recognise that he’s starting out on a journey that will be amazing. It’s exciting and overwhelming. It’s funny, on the day Matt started shooting, there were photos released. I hadn’t expected it. It was up on the internet so I went and had a look. I was genuinely surprised and excited. That doesn’t mean when it comes on telly I won’t be going, ‘Oh he’s better than me!’. At the moment I’m just really excited to see what they do next.”

Doctor Who has been a huge chunk of your life hasn’t it?
“Absolutely and a very special time. I’ll always look back on this time very fondly. Life changing yeah, and unique, it will be unlike anything else I’ll ever do. With the appeal it has and the range of attentions it gets it’s pretty unique.”

Have you taken any mementoes?
“I haven’t taken anything from the set though I got given a sonic screwdriver. And I got given some versions of the costume, then panicked and had to put them somewhere else because I thought what if my house gets robbed or burns down. I can go visit them I suppose.”

Did you have any fears about this being your last hurrah?
“Clearly you want your last one to be big and special and feel epic. And feel like an end to something. But as soon as I read the script I knew that was going to happen. Russell T Davies has managed to create a story quite unlike what we’ve done before. I just wonder how he keeps managing to re-invent things. But he does it and my admiration for him grows and grows.”

Is there anything you won’t miss about being Doctor Who?
“Not really. There are two sides to Doctor Who and I never anticipated being a celebrity – it’s not something that sits very easily with me. So there are sides to that I won’t be sorry to see the end of. So if some of that died down a bit that would be ok.”

Will you be sitting down watching on Christmas Day and New Year’s Day?
“Yes along with the millions of others – I gotta keep the viewing figures up. My family enjoy watching it with me – they enjoy the hoo-ha of it. There’s undeniably something special about being a part of something like a TV event. People talk about the Doctor Who Christmas special being like the Morecambe and Wise Christmas specials. But we’ve only done four and it’s a relatively new thing. My first episode was the very first Doctor Who Christmas special they’d ever done. I feel very chuffed that we’ve become part of the Christmas furniture and the family, like me, enjoy that sensation.”

Doctor Who: The End Of Time parts 1 and 2 will be shown on BBC1 at 6pm Christmas Day and 6.40pm on New Year’s Day.