Change isn’t hard. Doctor Who depends on it. If you count the very first story, in which viewers in 1963 had to get used to an eccentric, cranky old professor whose first adventure took him to prehistoric Earth and saw him apparently willing to murder a caveman if it would help him and his friends, we’ve had to learn to accept twelve different alien faces.

So a regeneration story by now is something the show has mastered — done eleven times already in different ways, many of them wildly successful. It was a radical move in 1966, but today it’s old hat.

Wearing the old hat, or more often the old coat, is old hat, too. Still, it’s surprising to think back and realize that only once before in the program’s entire history has the new Doctor spent his first half hour of post-regenerative trauma impersonating his previous self. Erratic behavior, yes; lapses into coma, yes; bad jokes, amnesia, yes, yes, and once even an attempted murder, but only once before have they tried (and it seems so obvious if you think about it) to bridge the gap by having the personalities overlap. And even then, because they weren’t sure when they wrote it what the new actor was going to be like, it was a complete accident.

I don’t think it’s an accident here. For the first half hour or so, Peter Capaldi does Matt Smith. Or more accurately, Steven Moffat is writing for Matt Smith. The jokes aren’t Capaldi jokes, they’re Smith jokes. I’m not saying Capaldi shouldn’t flirt, but he definitely should not flirt with dinosaurs. I’m not saying Capaldi shouldn’t do wacky, I’m saying he can’t, or at least he doesn’t. The lines don’t work.

As a result, we have the dizzying, awful feeling that Clara has, that the floor’s dropped from under us. He’s not only not the same man, he’s the wrong man. A stranger’s wearing his shirt and his manner and neither fit. Which means we have only a lizard, a potato, a teacher, and — well, okay, a housemaid slash ninja to save Victorian London from whatever is capable of incinerating a dinosaur and making it look like an accident.

Just about everyone you know who saw “The Eleventh Hour” will tell you they were sold on Matt Smith by “fish fingers and custard.” Steven Moffat can sell you a new Doctor if he wants to, and he doesn’t need 80 minutes to do it. So I don’t think he wanted to. The Smithisms are deliberate.

They set up a palpable switchover about the time the new Doctor discovers he’s Scottish and can really complain about things now. It’s the same time the new Doctor discovers he’s willing to swap a tramp’s most useful possession, his source of warmth, for something the tramp will have trouble selling and will never need, a means of telling time. Maybe something the Eleventh Doctor would do. But probably not.

It just gets better from there. For all the worry about how Clara and the new Doctor would work together, they mesh perfectly, by not meshing at all. They make good partners-in-crime; it’s the friendship part that’s tough.

Last time we had a prickly new Doctor argue with his companion a lot, it was just unpleasant, but Moffat has written sitcoms, which are nothing but pleasant arguments. Either because she’s no longer a mystery, or because we’ve had a year of her not quite working perfectly, or just because of the new comfortable discomfort, Clara really starts to sing from the restaurant scene onward, and Coleman turns in some of her best acting for the show yet.

I’m not entirely convinced that she’s the egomaniac control freak the Doctor thinks he sees; to me this seems like more of a Moffatism, characters diagnosing each other with psychological disorders they don’t actually demonstrate, the way we had “psychopath” defined last season as “a warm, affectionate person who enjoys doing somewhat daring things.”

Here she’s just brave, quick on her feet, sure of herself, able to learn from her own mistakes, and, by the end of the episode, willing to adapt in big, significant ways.

And then there’s Capaldi, who just over 30 minutes in settles perhaps not into THE way he’ll play the part (as his interviews perhaps modestly disclaim) but definitely A credible approach. Unsurprisingly, he’s graver, angrier, more forceful, even more physical, yet still dryly funny. He’s a fine actor. It’s not clear he has (or, arguably, needs) the breadth Smith displayed at the best of times, but he might have a greater depth.

So, unusually for a regeneration episode, does the story. On the surface it’s a sequel to “The Girl in the Fireplace,” of course; though the Doctor himself never quite remembers where he’s met the clockwork robots before, we naturally do.

Here they’re not just stealing parts for their ship, but also for themselves. They’re like brooms, says the Doctor to the head robot (who is, confusingly, dressed as the Great Intelligence) — replacing bits of themselves as they wear out, till eventually they’ve replaced every part of themselves and are no longer the same broom.

Which is basically what the Doctor’s done. He’s replaced his face, his voice, his hair, his body, his clothes, his personality, and even some of the lighting and furniture in his TARDIS. The blue box remains basically the same, and that’s about it; the screwdriver only dates back one face ago. Is he the same broom? Or just sweeping the same floors?

Certainly the manner of the sweeping has changed. There aren’t many moments in Doctor Who‘s history that feel like the scene where he pours two drinks and confesses to the head robot, “I have a horrible feeling that I’m going to have to kill you.” Or the one where it’s implied that this may very well be exactly what he’s done.

Then there’s that coda. “Missy.”

Look, I have no inside information, so this isn’t a spoiler, and Moffat’s notorious for leading us down the garden path on these things, but I can’t help thinking of another recurring character in Doctor Who who was also introduced in the classic show’s eighth season and later made a habit of being listed in the credits using eccentric but obvious aliases. Nor can I help thinking of all the hoo-hah about the Doctor being a woman this time, and how thanks to “The Doctor’s Wife” it’s now canon that Time Lords can change sex when they regenerate. I’m just saying.

Oh, and that one time the Doctor acted like his previous incarnation for about half the story? “Spearhead from Space” — the transition from the Second Doctor, on whom Matt Smith reportedly based his own portrayal, to the Third Doctor, on whom Peter Capaldi has apparently based his costume. I’m just saying.

I’ve only scratched the surface here — talked as little as possible about the increasingly forced comedy and even more forced profundity of the Paternoster Gang, implied very little about the Doctor’s redefinition of his relationship with Clara, touched not at all on the intriguing talk of “promised lands” and “heavens” (which the Doctor wants to reach but doesn’t believe in), not even mentioned that lovely phone call at the end. (Not one word of complaint about the worst theme tune revision in the new series, though the graphics are all right.) In a 76-minute story (certainly at least tied with “Day of the Doctor” for the longest unbroken Doctor Who episode), there’s bound to be more than one bucketful in the well.

So here we are at the start of a new cycle of regenerations. The Twelfth Doctor is really the First Doctor. In a way we’re back to basics. In a way it’s a brand new broom.