Suddenly the ethos of Season 18 starts to come into focus: this, like Meglos, features a conflict between two opposing factions: the questioning of the Outlers and scientific enquiry of Dexeter versus the authority and received wisdom of the Deciders. It’s all done with much more conviction than Meglos, though with fewer jokes, and the combination of a serious-minded script and some real effort in production makes this easily the best-looking and most coherent episode of the season to date.

On the production side, the location work is lush, with some of the plants in Black Park painted in exotic colours to suggest the kind of alien jungle the show’s normally attempted in studio. There’s a real scale to the brief shot of the distant starliner, and to the Alzarian village, with young men swimming in the lake, and piles of river fruit being harvested: a hint of the idyll about to be disrupted by mistfall. When that comes, some judicious use of dry ice and dusky lighting really sells the atmosphere and menace, especially as the backlit Marshmen begin to rise from the water in a sequence that might have been inspired by The Sea Devils, but betters it. This is as good as the series has ever looked.

The flipside is, again, the perennial JNT issue of getting the Doctor involved in the story. Again, he and Romana spend nearly the whole episode locked in the TARDIS doing repairs until Adric bangs on the door. Even then, they don’t actually interact with any of the other characters. At least there’s a purpose to this: Romana’s reluctance to return to Gallifrey, and the Doctor’s curious resignation that their time together is about to come to an end:

ROMANA: Doctor, I don’t want to spend the rest of my life on Gallifrey. After all this.
DOCTOR: Well, you can’t fight Time Lords, Romana.
ROMANA: You did, once.
DOCTOR: And lost.

The Doctor’s passivity – recalling his similarly diffident attitude towards Sarah Jane last time the Time Lords came calling – and Romana’s teenage surliness (throwing herself on her bed and sighing heavily) don’t quite work for me. These two defied the Gods of Darkness and Light in Time, I’d at least expect some more fight. Plus Romana’s bedroom looks like the lighting section of Homebase (so many lamps).

And then there’s Adric. Well: it’s a tough part, a completely new type of companion and the production makes little effort to endear him to the audience. He’s an earnest swot who bullies a girl and pushes over an old man, before showing off his intelligence to Romana. Apparently he was envisaged as an Artful Dodger type character, but the Artful Dodger was a plucky underdog, picking the pockets of London’s elite. Adric, as he’s anxious to point out, is an elite. You can’t have it both ways. I’m not sure this contradiction is ever resolved.

Next episode: Full Circle – Part Two