By rights, putting that much slapstick in an episode of Doctor Who should have irritated the socks off me. Yet, even now, I’m chuckling at the puerile Thomas Thomas gag. How did The Crimson Horror get away with it? I’m not sure, but I think it has something do with its richness; in its inventive and elaborate structure, its unwatchably horrific goriness, its daring backstory and clever plotting, its drama and its fabulous characters. The slapstick is a part of that: more everything means more comedy. It just works.

Since coming back as 45 minute episodes, Doctor Who has had issues with pacing. Introducing a whole new environment, new characters, telling a story and wrapping it all up is a tall order for the time available. The pacing has ended up uneven. This mini-season has taken quite a successful approach: minimising the story to allow some atmosphere to develop and give it room to breath. But even then the stories have been too thin; each one has had some obvious padding just to sustain it to the full 45. Somehow, in The Crimson Horror, Mark Gatiss has condensed a satisfying saga with a goodly group of protagonists and made 45 minutes feel feature length.

For the first 15 minutes I was convinced we were getting a Doctor-lite episode (see also Love & Monsters, Blink, Turn Left, The Girl Who Waited). That’s fine with me, I always enjoy those. It also appeared to be a stealth pilot for a full series of The Veiled Detective. Also good. On the strength of that 15 minutes, I’d happily watch the full series.

Diana Rigg was excellent (yes, perhaps a little OTT, but forgivable in the circumstances). She may have developed disappointingly reactionary views but she’s still got it in the acting dept. And I adored Catrin Stewart’s tribute to Mrs Peel’s leather-clad action heroics. Even better was her real life and onscreen daughter Rachael Stirling. The episode was properly scary, too – the processing (and failed processing) was quite horrific.

Continuity corner: we get a major (and rather surprising) Tegan reference. It seems remarkable that in 2007 calling the crab monsters The Macra seemed daring for its unusual admission of 20th century Who continuity, and now we’re getting throwaway references the gobby Australian. But I’m still utterly delighted that we can have scenes in this one carried by a members of the Silurian and Sontaran races (introduced 1970 & 1973).

So I could list the niggles: the sepia-film flashback style laid it on a bit thick (though the condensed setup was effective), the optograms (the effort made to make these seem credible made them less so), surviving the rocket launch trapped in the shaft, etc. etc. It doesn’t really matter. (I don’t think I even picked up what the actual purpose of the processing was…) This story was fabulous.

I even enjoyed Angie and Artie’s Clive Banks moment. But I hope that Clara makes the obvious assumption about a picture of her in Victorian London: that she will go there in her (personal) future…