THERE is a moment near the beginning of the second episode of the new series of Dr Who when Rose, the Doctor's pretty sidekick, attempts a Scottish accent. Held at gunpoint by a procession of 19th-century Scottish soldiers, she tries out a pitiful "hoots mon" and is quickly shushed by the Doctor, who then proceeds to converse with the soldiers as if he were one of their own.
Which in real life, of course, he is. Indeed it is perhaps one of the only times in the new series that viewers will get a hint that the latest Dr Who hails from Paisley, rather than the distant planet of Gallifrey. On this sunny Thursday afternoon in Glasgow, however, David Tennant - television's newest Doctor Who and quite possibly the only one to also have played the role of Casanova - is wearing his Scottishness on his sleeve, excitably leaping up to thank everyone for coming and telling them how much it means to be able to bring the Dr Who team (Billie Piper - with boyfriend Amadu Sowe in tow - Russell T Davies and an assortment of writers and CGI folk are here too) to Scotland. Tennant even utters the word "jings".
We're all here to watch "Tooth and Claw", an episode from the new series that is set (although sadly not filmed) in Scotland. It is a terrifying romp through the gloaming that features Queen Victoria (played by Pauline Collins, aka Shirley Valentine), a particularly fearsome werewolf, and some monks who have clearly rented Crouching Tiger Hidden Dragon one too many times. Beautifully shot, stylishly executed and also rather funny, it proves that Sydney Newman's 1960s creation is most definitely still on form, even if his main character has changed in both shape and voice over the decades.
Tennant adopts a mockney twang for the role, a move that has led to accusations that it was deliberately changed for a world that wasn't ready for a heavily Scottish-accented Dr Who. It's a charge both Tennant and Davies deny.
"It didn't bother me one way or another," says Tennant. "It doesn't make me any less Scottish not doing a Scottish accent. But it was nice to have one episode where Russell came up with the idea of the Doctor having a Scottish accent - which remarkably the doctor could do..."
Davies, for his part, strenuously denies that it was a result of any sort of BBC dictat. "I absolutely swear to you on my life!" he protests.
In fact the writer is obviously a Tennant fan. He gave, Davies says, "one of the best auditions I'd ever seen" for Casanova - another Davies vehicle - and, since then, the writer had kept him at the back of his mind for the Dr Who role. He seems thrilled with his choice.
"He's fantastic," says Davies. "The thing with great actors is that you don't know quite what you're going to get. They always take you by surprise."
The feeling is obviously mutual. "I'm delighted to be doing [Dr Who]" Tennant says. "It's a huge thrill and a huge privilege. It's been a fantastic nine months, it's been a really special time."
He happily defends accusations that "Tooth and Claw" is perhaps a little too scary for some of Doctor Who's younger audience members. "Aaah come on," he says, his voice lapsing into pure Paisley (his father is the Very Rev Sandy McDonald, a former Moderator of the Church of Scotland and he is a former alumnus of Paisley Grammar). "He pushes it quite far but it's still responsibly done. It's a fantasy environment and children understand that too.
"Part of growing up is being scared. That's what all Doctors have done since 1963. I mean, there's no blood. I think it was just far enough."
He says he loves the diversity of the role - the fact that the characters can move from the year five billion to the 1870s from week to week - but admits that some of the plot lines, and the indubitable fact that he is not Christopher Eccleston - may not appeal to everyone.
"A show like this receives so much attention and so much analysis, you're not going to please all of the people all of the time," he says.
Piper, meanwhile, is diplomatic when it comes to comparing her new doctor with Christopher Eccleston, who left at the end of the last series.
"They're different people," she says. "They're going to bring different things to the role. David's doctor is a lot more emotional, whereas Chris's was more intense. David is quite light-footed whereas Chris was more deep-rooted. They have different approaches."
As for the process of a working relationship with Tennant, Piper describes it as "an organic thing. A new person rubs off on you".
"We only had a week to rehearse, but I just think we found a natural groove. That's what happened. It seemed to work perfectly, it just happened and we got on with it."
So has Tennant ever worried about being typecast? "I did remember being thrilled to bits when I got asked and then a few days later thinking, 'oh, is this a terrible idea?'" he says.
"But that didn't last very long. Time will tell. The only option is you don't take these jobs when they come up. You've got to just roll with the punches."
There has been speculation about Tennant's love life (he's been pictured with Thunderbirds actress Sophia Myles and there were rumours about a relationship with actress Keira Malik), and he obviously struggles with the attention. "No-one teaches you how to deal with all that sort of stuff," he says. "You have to decide for yourself where the lines will be drawn. It's about your own personal integrity. You just have to figure it out as you go."
He says he's keen to do theatre again - he trained at the Royal Scottish Academy of Music and Drama and has a background at Edinburgh's Royal Lyceum, the RSC and the Donmar - and says he'd love to do something at the new National Theatre of Scotland.
"Nine months of the year you're filming, so it's difficult to do anything else," he admits. "But I fully intend to go back to the theatre at some point and, if it was something for the National Theatre of Scotland, all the better." As for a third series, both Piper and Tennant have signed up, although there is speculation over whether Piper will appear in every episode.
But that's all still some time away in the future. So what can you look forward to in this latest series?
Well there's a peek inside the Torchwood Institute, domain of Captain Jack and the place that, later this year, gets its own spin-off series on BBC3. Then there's your usual scientific cats, men who turn into werewolves, an episode where Rose and the Doctor fear they may never return to Earth, and a fair few close-to-the-bone jokes about the bloodlines of the Royal family that have anti-royalist Davies's pawprints all over them.
Shame really. "They're fans of the show," Piper says at one point, turning excitedly to Tennant.
Well, they were, at least.