There’s something very Dennis Wheatley about this story: of burnt-out businessmen who have presumably had their fill of worldly pleasures and have started to dabble in the otherworldly as an easy route to the success that has eluded them. The domesticity of the villains, and their disgust and incomprehension at what they’ve unlocked, is a new angle on sci-fi horror only hinted at by The Dæmons, where the Master’s plans for universal domination prevent it from being quite so thrillingly mundane.

Lupton, the greediest and bitterest of the lot, naturally becomes the host for the demon spider the coven has summoned up, lurking on his back like a succubus. John Dearth’s voice, like a sarcophagus opening, and his wonderfully expressive face (smug when condescending to the other coven members, panicked when pursued by the Doctor) are brilliant, and make what could have been a fairly underwhelming villain in the late Roger Delgado’s absence into something much more interesting.

Most of this episode focuses on Lupton’s one-man infiltration of UNIT HQ in pursuit of the Metebelis crystal where he interrupts a comedy sequence of Sarah Jane (cosplaying as Amelia Pond) explaining what she saw at the meditation centre, and ends with a chase by car, helicopter, boat and hovercraft as Lupton makes off with the stolen crystal. I think this sequence has got a lot of stick over the years, and I suppose it is quite self-indulgent. But for an era that’s pushed the show’s boundaries (and budget) for action sequences, it does make sense to try to cap it all in the final serial.

Apart from the flying Whomobile, which feels like a joke too far in a sequence that already includes a comedy policeman and a surprised tramp, I think this chasing around makes for a dynamic episode, and suspect it’s only when you’re trying to watch the story in one go that it feels like it’s getting in the way of the plot. It’s a shame, though, that Barry Letts’ direction fails to make it clear that the cliffhanger involves Lupton being teleported rather than falling out of the boat.

Next episode: Planet of the Spiders – Part Three