This has the style of The Time Monster done right – bantering scientists; advanced equipment in a country house; ancient glowing artefacts wreaking supernatural havoc on hapless passers-by; the whiff of something unethical that needs covering up, and Pertwee-years yokels. It resurrects an interest in the origins of humankind, and has some attractive folk horror overtones.

I really enjoy how stylishly this is directed in contrast to The Invisible Enemy: the mix between the glowing skull and Wanda Ventham; the rare night filming, and a superb double-cliffhanger as Leela is apparently shot while something horrible advances (via tracking shot) towards the Doctor. It’s absolutely spot on for a Halloween episode.

Like Chris Boucher’s last script, for The Robots of Death, this keeps the Doctor and Leela out of the main action for the entire episode, to similar effect. We understand some of the characters and relationships within Fetch Priory before everything goes to pot (I particularly enjoy the lightly flirty relationship between the frivolous young Adam and a black-haired Wanda Ventham, looking like her own evil parallel universe double), and see that Fendelman and Max are up to something sinister. Plus, with Dennis Lill’s Salamander-meets-Zaroff accent we have our second vaguely Germanic professor in two stories.

Meanwhile, the Doctor and Leela get to mooch about and have fun in the countryside, which is thoroughly charming. Their gentle squabbling during the opening scene in the TARDIS plays as cute and witty (I love the Doctor trying to change the subject by complimenting Leela on her new dress) rather than antagonistic – it’s the kind of thing I think they were pitching for with the Doctor and Tegan/Peri, but it works. Tom looks great in this: I think he’s had a haircut, and it shows off his ginger sideburns. Dashing around the console, scarfless, long velvet coat flapping, shirt open, he’s never looked more like the romantic adventurer.

Next episode: Image of the Fendahl – Part Two