Terrance Dicks’ love of continuity is starting to crop up in the scripts. Here, when the Doctor comes round he rambles about Victoria. Later, he tries sulfuric acid on the seed pods, which feels like a call-back to The Krotons. We’re moving from the Doctor being a wanderer in the fourth dimension with, aside from the Daleks and Cybermen, few links between stories, to a series with a recurring guest cast, and greater interconnectedness.

Given the clichés it has to play with (aliens needing a foothold on the moon before attacking the Earth, and weather control, just like in The Moonbase; water as the solution to the alien seeds just like in the 1962 adaptation of The Day of the Triffids), this is very engaging. The film studio work with Troughton is impressive, and very funny, and the return of the foam machine gives a good idea of how great it must have looked in the earlier story.

The strongest character work is reserved for Fewsham. He’s finally compelled to turn against the Ice Warriors and help in the fight to save the Earth, transmitting the vital details of the Martian invasion, and paying the price with his life. It’s been a great, un-showy performance from An Age of Kings‘ Terry Scully, bringing his experience of playing weak men pushed into positions of power far beyond their abilities, and only at the last finding the strength to do the necessary. The way Ferguson directs the sequence – flipping between the moonbase and the same images relayed to a monitor on the T-Mat London set – gives these scenes a real immediacy and poignancy as Fewsham’s colleagues, who’ve just dismissed him as a traitor, helplessly watch him being gunned down.

Next episode: The Seeds of Death – Episode Six