It's good to be David Tennant. Maybe he's not the most handsome actor on the block - tall and skinny, with an angular face and auburn hair. And maybe the general public still have only a passing familiarity with him.
Nevertheless, this 34-year-old actor can lay claim to a dazzling roster of work in the past year, and his good fortune is about to multiply, with enough juicy roles to leave fellow-thespians drooling. There's been an award-winning theatrical performance (as Jimmy Porter in John Osborne's Look Back in Anger), a show-stealing part as Sarah Parish's detective lover in the BBC's drama series Blackpool, and the title role in its Casanova. Next, he turns villain for an ITV thriller Secret Smile, based on a Nicci French novel. He's also snaffled a part as Voldemort's henchman in the latest Harry Potter film. And then comes the role that will surely see him tip the balance from esteemed actor to household name - the new Doctor Who.
All this from an actor who barely registers on the celebrity scale. He leans back in his chair on the terrace of a Mayfair café without causing a flicker of recognition among passers-by. He wants to talk about his latest project, Secret Smile, which sees him playing Brendan Block, a "deeply misunderstood" individual, Tennant says, with typical understatement. In fact, Block is an egomaniac who refuses to accept his girlfriend's ending their relationship. Instead of sloping off like any self-respecting rejected lover, Block returns with a vengeance, starts going out with his ex-girlfriend's sister, and wreaks havoc on her family.
So, who is David Tennant? The amiably eccentric Timelord, Orton's angry young man, or does he have Block's dark, villainous side? "God, no!" he laughs. "There's no dark side of David Tennant. I'm completely pure and clean. But I think everyone understands what it feels like to be dumped." He coyly admits to past obsessions with the opposite sex. "It's always a very intoxicating and irrational thing to be that obsessed with someone. I hope I dealt with it better than Brendan Block." He felt grateful, he says, for his single status during filming. "It would have been a nightmare if I'd been breaking up with someone while playing Brendan..." He liked the role because it felt vaguely Hitchcockian, and he loves the darkness of films such as Marnie.
For someone "pure and clean", he certainly likes art and literature that examines the bleaker side of life. Occasionally, his characters' bad habits have crept into his life. Osborne's Jimmy Porter was one example. "I didn't become any more furious than normal, but I did become deeply politically incorrect. That's what Jimmy does, he pushes the boundary and then goes beyond it. I was being rude at really inappropriate moments."
Rudeness doesn't come naturally to Tennant. He is, after all, a minister's son. His father became the Moderator of the Church of Scotland - "that's our equivalent of the Archbishop of Canterbury". His mother looked after him and his older sister and brother as they grew up in Paisley amid the usual bustle of a minister's house. "There were always people dropping by, but it was what I'd grown up with so I never thought, how odd, why isn't my father going to an office?"
Tennant went to Paisley Grammar School, where he suffered the academic work rather than enjoyed it. All the while he talked to his closest friends about his ambition to be an actor. With uncanny prescience, he told them that one day he wanted to play his hero - Doctor Who.
He has already filmed his first lines for this childhood-fantasy-come-true. When he arrived on set to film, only a skeleton crew remained. The last episode of Christopher Eccleston's Doctor Who had just been filmed, and there was an end-of-term feeling to proceedings. "There was hardly anyone there, and yet you're sensing the importance of the moment. My first line was, 'Hello! New teeth, that's weird.' It was very odd, saying my first line as the Doctor."
Whovians out there are already wondering what sort of Doctor Who he will make. "I don't know how I'm going to play it yet," he laughs. One thing's for sure: the Scottish actor will be putting on an English accent for the role - a fact that has already roused heated debate in Scotland. "There'll be a bit of a story behind my English accent - it's not that straightforward. But anyway, I'm used to doing English accents." Does he object to having his Scots brogue stripped from him, as some reports have suggested? "No. I don't feel any great nationalistic need to be Scottish. I am comfortable with my background.
"But I don't understand why there's this thing that actors from a certain place have to speak with the accent of where they come from otherwise they're somehow being un-Scottish. That feels very 'small nation' to me, and I think Scotland's a much bigger nation than that."
Roused from his early-morning languor to a state of almost crossness, you can suddenly see why directors respond so well to this actor. He is charming even when angry. Testament to this charm is the way that he won the plum role of Doctor Who after impressing its writer, Russell T Davies, when he worked with him on Casanova. But Tennant does talk about the weight of responsibility that comes with playing the Doctor. He knows people care passionately about the series and have big expectations of any actor in the role. In the past, pressure like this has led to moments of desperation for Tennant. He admits that every job has its low point when the nerves crash in. "That's a regular visitor. I end up thinking: this will have to be the last job I do because, obviously, I'm messing it up so badly. Everyone else on set always seems much more relaxed and confident than me.
"I think that it's part of the psychology of what you do. You get used to it. But when you're in the midst of it, it doesn't feel like a part of the process, it just feels horrible and desperate."
The worrier in Tennant must cope with the rise in fame that will inevitably follow his new roles. No more mornings sitting undisturbed outside Mayfair cafés. "I never ticked the box saying, 'Want people to come up to me'. But as long as people aren't unpleasant or violent or rude, then I don't mind. I think you look very poor if you start complaining when you're so lucky to be doing this job."
These concerns about fame are a far cry from his humble beginnings in acting. He was christened David McDonald but told to change his name by Equity to avoid confusion with another actor of the same name. He happened to read an article about the Pet Shop Boys' Neil Tennant, and thought that name would do. After drama school he went on to repertory theatre, touring Scotland in a van and making periodic attempts to win a part in Taggart - a goal he never achieved. Things began to turn around after he headed to London and moved in with an acting colleague, Arabella Weir, who was poised on the edge of Fast Show success.
The change in his own fortunes has come gradually, so he has had time to get used to his success. "I think I'm probably ambitious, but I've never had a long-term plan. I've just thought, I hope the next job is good. I don't know how else to be because you don't really have that much power in acting." Even now, with so many roles coming his way? "I suppose now there's an element of choice involved, which is a wonderful place to be."
And, presumably, the once- penniless actor has now got a very happy bank manager. "Oh, I've done nothing with the money yet. Maybe I'll store it up for the future when I'm back working in Dundee rep." Somehow, you know that's not going to happen.
The new series of 'Doctor Who' starts on Christmas Day on BBC1 at 6.15pm; 'Secret Smile' begins on 12 December on ITV1 at 9pm