Having revealed its monsters, the story proper kicks in, and it’s pretty good actually. Most interestingly, writer Derrick Sherwin finds something new to do with the Cybermen – in danger, in The Wheel in Space, of becoming little more than lumbering robots. He adds an insane Cyberman, overwhelmed by emotion, stumbling about with arms flailing madly like a Universal Frankenstein’s Monster, and screaming horribly. It’s by far the most disturbing thing anyone’s thought to do with them since The Tenth Planet, using their residual humanity to overwhelm their computer brains: it’s such a neat concept that Tom Macrae essentially revisited it in The Age of Steel. This almost makes up for the sweet moment when another Cyberman is seen carefully helping its colleagues climb down a ladder into the sewers.

Elsewhere the story is a natural bridge between The Web of Fear and the imminent Jon Pertwee years. The Brigadier mentions the Yeti, and a few minutes later we have an explicit homage to that story’s most memorable moment – Cybermen in the sewers rather than Yetis in the Underground, but it’s basically the same. And, foreshadowing his frequent role in the next few seasons, for the first time we get to see the Brigadier butt heads with one of his civilian superiors, before he steals the female companion’s clever idea and patronisingly tells her it’s man’s work to see it through. Then acts surprised when ‘those crazy kids’ ignore him and go off to try for themselves.

All of this begins to show how Sherwin’s vision for a reformatted Doctor Who might work: the Doctor as the eccentric genius flitting round in the background; the female companion being smart and active, but getting into trouble, and the Brigadier trying to hold it all together and providing the backup muscle for both. This might even have tempted Troughton to stay for longer, if it had reduced the pressure on him to be the leading man – something he seems to have been ambivalent about. In the event, Pertwee’s “I’m the star” performance works against the idea of the Doctor being a member of the band rather than an artiste with a backing group

Next episode: “The Invasion” – Episode Six