‘Everything ends, and it’s always sad. But everything begins again too, and that’s always happy.’ The return of showrunner Moffat, who was supposed to have bowed out with The Husbands of River Song but has been persuaded to stay to fill the gap between Chris Chibnall finishing Broadchurch and taking over Doctor Who. Perhaps wisely, he elects not to launch straight into the adventures of Bill Potts, but to revert to the status quo ante Clara when the companions were rarely a fixture of the Christmas Specials.

His farewell tour begins with a riff on the popular superhero genre, with the Ghost / Grant Gordon a cross between Superman (the whole Clark Kent thing) and Batman (the gravelly voice, and the leathery costume) created by accident thanks to the Doctor crashing into a child’s bedroom. This plays into standard Moffat tropes – the Doctor gets cookies and milk instead of fish custard, but here’s another in the list after Reinette, Amy, River and Rupert whose lives are permanently altered because they encountered the Doctor at an impressionable age (tell me about it). I could have done without the other trope of a man stalking a woman until she falls in love with him (he even moves into her house – bit creepy).

The set-up is familiar, and it plays out with a little less ambition than we might have expected given Moffat’s been granted a bonus throw of the dice. After The Husbands of River Song it’s back in sitcom territory, with Harmony Shoal returning and posing exactly as terrifying a threat as they did last time. Lucy Fletcher could be Moffat running with RTD’s Penny Carter character – the names have the same cadence, they’re both journalists who infiltrate a corporate headquarters and encounter the Doctor on a similar mission. These scenes are as fun as their equivalents in Partners in Crime, and the presence of a beloved comedy actor as the new companion (Tate/Lucas) makes the comparison irresistible.

Nardole is a neat addition: he can neatly balance absurd comedy (‘I ruled firmly, but wisely.’) with the ability to talk to the Doctor directly and honestly (‘You cut me out of Hydroflax because you were worried you’d be lonely.’) Plus, Lucas is clearly enjoying himself: he loves doing the companion “GASP! Doctor!” bit when he spots the security drones on board the spaceship, and the little “Wahey!” when the Doctor does one of his hero moments. Anytime he and Capaldi are on screen together the episode is at its best.

The problem is, they spend a lot of the back half shunted into their own side plot on board Harmony Shoal’s spaceship while Grant and Lucy get all the romcom stuff in New York. I don’t think this does either plot any favours: even though it’s well written and structured, it doesn’t have quite the oomph of some other Christmas specials. But even as a lesser Moffat story there’s a lot to enjoy – particularly the 12^th Doctor, whose egregiousness is now a distant memory. I love how he dismisses Brock as an irrelevance once his plan has failed. Like all Moffat scripts, you kind of have to ignore any implications for the wider continuity of the show (“Why doesn’t the Ghost make the Doctor redundant?” can be filed alongside “Why doesn’t the Doctor just go back and change the past so things work out all the time?”) and just accept it.

Next Time: The Pilot