It's 1975 in Paisley. A little boy is playing in his garden, and he's excited because his granny has knitted him a really, really long scarf that makes him look just like Doctor Who. He wants to be the Doctor when he grows up. In fact, he tells everyone, he will be the Doctor when he grows up. It's just a little boy's dream. Harmless, really.
Fast-forward to 2005 in Cardiff. A grown-up man is excited because he has just seen the new Cybermen for the first time. He is playing Doctor Who in the new series, and is telling everyone it's the most thrilling thing that has happened to him ever, ever. It was all a little boy's dream. A dream that came true.
Even David Tennant can't believe the story sometimes: the boyhood fantasy being lived out 30 years later. When he talks about his new job, he rabbit-drums his feet on the floor and rubs his hands through his hair so it frizzes up like electric wiring. "It's reeeaaallly exciting," he says. "Apart from anything else, it's fun. It's a laugh. You've no idea. It's such a laugh." And then his brown marble eyes go kind of cloudy as he remembers the little boy again. "It really takes you back to tattie scones in front of the telly."
He does actually say tattie rather than potato, because Tennant is still, in case there was any doubt about it, very Scottish. Well, he is and he isn't. For his lunch he orders eggs benedict (there's chips on that menu, man). And although he's a west-coast man in his thirties, he hasn't even the slightest suggestion of a beer belly. Indeed, I've seen bigger wrists than that waist. Peter Bowker, the writer of the BBC drama Blackpool, said his skinny star could be ugly and handsome at the same time. Even worse, when Doctor Who fans heard he had won the role, some of them rushed onto the internet to slag him off. "He looks like a weasel!" wrote one, a tad hysterically.
"Well, I've never been boy-band handsome," says Tennant with a shrug as he munches on his eggs. "So my looks have never been an obsession of mine." He is even willing to forgive the weasel comment because most Doctor Who fans have been delighted by his casting and are frothing at the prospect of his debut in the upcoming Christmas special. Truth is, those fans should be pretty pleased they got him, because there were moments – mostly under the duvet at about three in the morning – when Tennant panicked and almost turned the role down. "When I was offered it, suddenly it was real rather than some kind of childhood fantasy moment," he says. "You suddenly start thinking, 'I have to do this now.' It was curious. It was almost a 'be careful what you wish for' moment."
The success Christopher Eccleston made of Doctor Who earlier this year must have made Tennant's decision easier, but it was still a shaky time for him. "You have to think through all the implications. I had a couple of wobbles about it. But then I woke up one morning and thought, 'What are you farting about for? Come on, this is not an opportunity you can let go by. To hell with what happens. I really want to do this.'"
Now he's said yes, chances are Tennant will make a fantastic Doctor – even if today, on a break from the set, he looks more like a graduate from the local polytechnic than from the Prydonian Academy on Gallifrey. Wearing a T-shirt with a clever slogan, a crinkly leather jacket and almost-trendy trainers, he seems like a pretty ordinary 34-year-old man. But then, unexpectedly, when he's talking about Cybermen or Sarah Jane Smith or something like that, there are invisible exclamation marks at the end of his sentences and a different-ness, a not-quite-here-ness, about him. If he can capture that on screen too, he'll be sensational.
Even so, the question of how to play the Doctor is not easy. You could do it dark and serious (like Tom Baker or William Hartnell) or light and big and silly (think Sylvester McCoy or Patrick Troughton). Tennant pauses to think about this, eggs benedict hovering near his mouth. "You've probably got to do both ultimately," he says, "because the Doctor does both."
The problem is that heroes can be utterly boring to play. Christopher Eccleston said the key to the role was making the sameness different. The Doctor never develops – he saves the universe. End of story. "There are elements of that I recognise," says Tennant. "You're finding ways to skin a cat each day. The Doctor is always right; he always knows where he's going; he has the moral high ground. He doesn't waver from that, so it's finding new ways to come at that. Part of the joy of the character is that he's unexpected. He's an alien and he's unpredictable."
Then there's the question of how Tennant's Doctor will sound. Eccleston used his own Mancunian accent ("On me 'ead, Daleks!") so now fans want to know whether Tennant will stay Scottish. "There's a bit more to it which I can't talk about because it happens in the second series," he says. "But no, initially I'll be doing it kind of the way I did Casanova, because the BBC said they'd like me to do it that way."
That's really about it on the role and how he'll do it. Quite frankly, he doesn't have the time to sit around and ponder his motivation anyway. For three months now he's been working 12-hour days, and he's got another few months of the same to go. When he won the role, he left his home in London and moved into a rented flat here in Cardiff, the city where Doctor Who is filmed.
He admits he was rather worried about leaving his life behind. "I was nervous about moving to Cardiff but I'm getting home to London on weekends, so I'm getting back and doing a bit of life. When you're here it's 12-hour days, and then you're learning your lines for the next one. There's a relentlessness to it – but I have a lot of friends who are actors, so they know the score. You fall in and out of each other's lives all the time."
As for relationships, and how they survive such a period of life-on-pause: well, Tennant isn't willing to talk about that. There were reports of a break-up with Keira Malik, the daughter of the actor Art Malik; more recently, smiley, hand-holding pictures have appeared of Tennant and Sophia Myles, who played Lady Penelope in the Thunderbirds movie and co-stars in one of the new Doctor Who episodes. Asked a few times in different ways whether he is single, he avoids answering, eventually smiling and saying: "Will I just give you the same answer I gave before?"
This awkwardness about discussing his personal life with strangers is not surprising: it's just not the kind of thing you do if you have a middle-class, middle-Scotland upbringing. Tennant's father, the Very Rev Sandy McDonald, was a minister and then the Moderator of the General Assembly of the Church of Scotland in the late 1990s. When I ask Tennant whether he is still a Christian, there is a long, long pause. "I'd say that's an ongoing question for me," he eventually replies.
Most of his family – his London-based brother Blair being the notable exception – are still in Paisley, so there is a cord pinging him back to the town fairly regularly. Earlier this year, his mother, Helen, was diagnosed with bowel cancer; a course of chemotherapy over the summer appears to have been a success. "She's very well now," he says. "Extremely well. She made a fantastic recovery, which was a huge relief to me."
Both parents were cautiously supportive when their son said he wanted to be an actor. He went to the Royal Scottish Academy of Music and Drama in Glasgow, graduating in 1991 and going straight off on one of those tours where the actors and props travel around in the same rickety van. There followed a longish time on stage and the occasional part on television, during which he became the kind of face people couldn't quite place but were convinced they knew from somewhere.
Then, last year, the incline of his career suddenly got steeper with the role of Detective Inspector Peter Carlisle in the critically acclaimed Blackpool, a bizarre mix of grubby crime drama and camp musical. He is extremely proud of it, seeing it as one of those programmes that took a step outside the normal and changed the schedules. "It was a real out-there thing to go for," he says. "I think TV is actually beginning to challenge itself and say, 'Hang on, we can't just go on making Heartbeat.' Not that there's anything wrong with Heartbeat, but you still get the Heartbeat sub-clones three generations down the line."
Blackpool led directly and quickly to the lead role in the fabulously naughty Casanova, written by Russell T Davies, who would go on to be the executive producer and writer of Doctor Who. Nobody knew it at the time, but Casanova was David Tennant's audition piece for the Time Lord.
If there is a theme to much of Tennant's recent work, such as the stalker thriller Secret Smile on ITV, it's probably sex. There was certainly a lot of it about in Casanova, and Tennant played it all with a kind of twisted-up sexuality. All of which might have made his casting in Doctor Who a little curious: after all, there is an ultra-clean innocence about the Doctor. He has a granddaughter, but there is never any whiff of sex on the floor of the console room.
"It's different now in the way Russell writes it," explains Tennant. "The relationship between the Doctor and Rose is a love story – except they're not shagging. He's on his own and yet he has Rose, but can they ever be quite a couple in the traditional sense? He's 900 years old and she's 19, and that would be a bit weird. That said, there are moments in this series that are … well, sexual would be the wrong word, but they explore that side of things possibly more than we've seen before."
On the subject of Rose, you can tell Tennant has already established a jokey, fun relationship with his co-star Billie Piper. "Billie Piper? I can't bear the woman," he says with a grin. "It's becoming quite problematic, actually. We never film at the same time. We have to be edited together afterwards. We can't be in the same room."
This silliness, this fun, is just part of the joy of the show as a whole for Tennant. He is having a scream every day. This week, for example, he has been to an alien planet ("bits of it were Wales, bits were special effects"), and he has another one to visit soon. He's loving the variety of it all. "You can be saving the universe and then talking about fly-fishing, but you've got to play it for the truth of the situation. You've got to believe that this guy can be talking about tangerines and then suddenly save the world."
What he really enjoys is the hugely old-fashioned good/bad struggle at the centre of the show. In fact, he sometimes wishes that the real world was a little bit like that. "Would that there was a Time Lord who could sort it all out," he says. "That's part of what's appealing about the show – he will always find a way of allowing the good people to triumph. Obviously, real life is a little more complex. But that morality is important. It's nice to see it being trumpeted, celebrated."
His love for the show is clear, then – but whether he has prepared himself for the love/adoration/obsession of the fans is another matter. The audience for Doctor Who has always been stereotyped into one obsessive image, and some of the fans can certainly become unhealthily focused, their universe spinning round one television show. At the moment, though, Tennant is willing to laugh it off. "I do hope I get a stalker. I won't feel I'll have made it otherwise. In fact, I'm going to have it in my contract."
More seriously, he is happy to see the positive side of obsession. "People are very invested in the show on quite an emotional level, and maybe that's partly because it often comes from childhood," he says. "Certainly, I grew up with it."
And now that he is grown-up and he is the Doctor and the dream has come true, he is cherishing every second, even though the schedule won't end until March or the beginning of April. It was exactly that kind of relentlessness that became too much for Eccleston, who walked out of the show after one series, but – at the moment – Tennant's intention is to do a second run. "It's my full intention to do the second series, but the viewing figures might tumble through the floor, and that would be my fault. Nobody else has changed," he says.
It's another self-deprecating, middle-Scotland moment from a man who appears to have little pretension. There's no actorly twittering; none of those irritating phrases you hear only on Parkinson. I tell him that one day, when he is sitting in a corner in a nursing home with a rug on his knees, perhaps in Paisley, someone will point at him most days and say: "You used to be Doctor Who." He laughs. "I hope so," he replies.
Dr Who and the Christmas Invasion is on Christmas Day, 7pm, BBC1.
Source: Mark Smith, The Herald