Peter Capaldi looks like he might be a good Doctor. But it's not easy being the Time Lord. Some actors have soared in the part, others have crashed down to Earth. This is our guide on how to get it right.
In Capaldi's first episode, Deep Breath, there are a few jokes about his Scottish accent but it's not the first time the Doctor has sounded Scottish. When he was played by Paisley boy Sylvester McCoy, he also had a faint Scottish lilt but confusingly when he was played by David Tennant, also from Paisley, he sounded English. Ideally, the Doctor should use received pronunciation, but Christopher Eccleston's Doctor explained his Mancunian accent by saying that lots of planets have a north. Perhaps lots of planets have a Scotland, too.
The right shade of darkness
Peter Capaldi says he wants his Doctor to be a little darker, which is a good move - after all, it's how the character started in 1963. In the first story, An Unearthly Child, the Doctor, played by William Hartnell, is narrowly stopped from smashing a man's head in with a stone just so he can save his own skin and get away in the Tardis. In another story in the 1970s, Pyramids of Mars, he callously shoves the body of a dead man out of the way. In another, Vengeance on Varos shown in 1985, he cracks a joke about a man dying in a vat of acid. He is not human. Remember that.
The right age
William Hartnell was 55 years old when he became the first Doctor in 1963; Capaldi was exactly the same age when he took over. If you are declaring the end of the universe or calling on the Daleks to end their invasion of Earth, you need to have a certain amount of gravitas. As Capaldi himself puts it: "There's a magic about the Doctor which is not about being in your 20s and 30s."
The right costume
Capaldi has got this one spot on: vaguely Edwardian but with an eccentric twist (in his case, DM-style boots) finished off with an elegant black jacket with a slash of scarlet lining. It looks like a tribute to Jon Pertwee, the third and possibly the most stylish Doctor.
It has not always gone so well though. Famous costume disasters were Sylvester McCoy's question-mark jumper, which suggested a kind of existential, knitted angst, and Colin Baker's bizarre mad clown outfit. Ideally, the Doctor should wear something that looks good but can also save his life (and in some cases the lives of everyone on Earth). Peter Davison's stick of celery, for example, worn on his lapel, could detect certain gases in the Praxis range of the spectrum, and on one occasion Tom Baker, the fourth Doctor, saved Earth from a nasty alien by tripping it up with his scarf.
The right education
The Doctor didn't go to the university of life, he went to the university of lives (he has 13). His education record on his home planet may not be good (he scraped through his final exams at the academy with 51% at the second attempt) so he ran away and discovered the universe for himself. "There's always something to look at," he once said, "if you open your eyes."
Again, all of this makes Peter Capaldi a perfect fit: he's intelligent, sharp and has been a fan of Doctor Who since childhood. After school in Glasgow, he studied at the city's school of art and has spoken passionately about his time there.
"It may sound nightmarish to some people now," he said recently, "but the government paid for you to be educated, because they believed it was a civic responsibility. I certainly would not be here, being Doctor Who, if they hadn't done that." (By the way, after struggling through those exams on Gallifrey, the Doctor also spent a time studying in Glasgow under Joseph Lister after popping back in time to the 1880s).
The right attitude to women
For the first 40 years, there was never any flirting in the Tardis and that was how Doctor Who fans liked it (they weren't getting any so why should some old, alien guy?) Then, Russell T Davies revived the show in 2005 and suddenly the Doctor was snogging people as well as saving them.
But could things be about to go back to normal with Capaldi and his 27-year-old companion Clara? "I think the Doctor is crazy about Clara," says Capaldi, "he loves her in a very deep way that is not just about romance. It goes to a deeper territory of affection." In other words, No Sex, Please, We're Gallifreyan.
The right values
The Doctor doesn't do politics but if he did, he would probably vote Lib Dem (because, like them, he's nice but sometimes has to work with the bad guys). If he does have a defining principle, it would be non-violence - he prefers books to guns - although he is absolutely not a pacifist: when a fight is needed, he's up for it. In one of his most famous speeches, he told his companions Polly and Jamie that there are corners of the universe which have bred the most terrible things. "Things which act against everything we believe in," he said. "They must be fought."
Could Capaldi be taking inspiration from that speech? In every picture we've seen, he is scowling, and remember, just under skin of the Doctor, there is Malcolm Tucker, the very different type of doctor (of spin) from The Thick of It. This new Doctor, says Capaldi, is going to be much less user friendly.