‘Oh, Doctor, you didn’t forget.’ Filling the gap between Seasons 18 and 19, this curio broadcast over the 1981 festive season is easy to mock, with its hilariously bad title sequence and theme music, a performance of incredible camp from Linda Polan, and the notion of a series of adventures for Sarah and K9 investigating the covens of England. There are, it’s true, numerous laughable elements, but the biggest surprise is that this works.

It’s essentially The Stones of Blood, (K9 aside) without the sci-fi elements. In some ways, in fact, it’s rather better than the Doctor Who episode. The prodigious night-time location filming is much more impressive than any amount of day-for-night work in the parent show, and writer Terence Dudley leans harder and more wholeheartedly into the folk horror elements than David Fisher did. Like The Wicker Man, at its core is anxiety around the failure of the local apple crop, with a return to the old religion and rituals to propitiate the local deity, Hecate. There’s a line of criticism that “everyone” in the village of Moreton Harwood – bar incomers Sarah Jane and Brendan, Juno and Howard – is part of the coven, but even that’s in keeping with the rotten community of Summerisle.

And it’s executed very well – Peter Howell’s sparse, eerie score is entirely appropriate for this spin on A Ghost Story for Christmas, and some of the sequences, particular Sarah’s near miss with a tractor on a winding country lane, are pure Seventies horror. The script isn’t sparkling, but the dialogue isn’t absurdly stylised – ‘Don’t be so touchy,’ growls the wonderful Bill Fraser as Sarah gets snippy, and it’s exactly the kind of thing that sort of character would say in that circumstance. True, the Bakers sound like they’ve wandered out of an episode of Howard’s Way, but that’s sort of the point of their upwardly mobile “place in the country” personas. Sarah’s credible fury at their patronising attitudes is the high point of a typically thoughtful performance from Elisabeth Sladen who, when not being called on to do unlikely judo moves, entirely recreates her classic role just without the element of a childlike friendship with the Doctor. The other actors, including Hellraiser’s Sean Chapman, are very good, and there’s a parallel universe where Brendan Sears was cast as a charismatic, charming Adric and the whole pitch of 1980s Doctor Who was different.

What’s not to like? The bizarre costumes Sladen is put in (including what looks like Tom Baker cosplay with a vast burgundy dress/cloak thing). And, strangely, K9 himself – he gets more to do than any Season 18 story, but is largely there as the butt of jokes, or as a handy laser gun. He’s easily the most dispensable thing in his own spin-off, which isn’t a great start. It must have been reassuring for the makers of The Sarah Jane Adventures to look at this and realise that Sladen plus a decent young actor or two were more than capable of fronting a series without the need for the tin dog.

This is earthier and more easily accessible than any Season 18 story, and a glimpse of a different take on Doctor Who in the 1980s: less experimental, more traditional and cosy, and perhaps a little bit more fun.