‘You can’t broadcast socially sensitive information unless you’re in control of the facts.’ An episode that essentially parks the Doctor and Tegan while it explores the ideas of Turlough’s repressed ancestral memories and Brazen’s attempts to maintain order as Frontios’ society descends into chaos. The result is Strickson gets his meatiest material, playing Turlough’s breakdown and recovery, and then, once again, overcoming his natural caution to face his fear beneath the earth.

For all Brazen sets up an inquiry, research and theorising hold no truck with him; he’s only interested in facts and certainty. He’s also a hypocrite when it turns out he’s been hiding the truth about Captain Revere for ages while berating Range for collecting his own information. You could argue the tribunal scene is padding, but I think it’s a helpful illustration of the tyranny Brazen represents and the dangers of a government that lies to its people in the interests of social control. When the people begin to reject Brazen’s heavy hand, he forces them out – as he does Cockerill here, leaving him to the mercy of the Rets, which come across like something from a 1980s cannibal horror as they descend on the outcast, and begin to move in on the colony itself.

There’s so much going on above the ground that the Tractators don’t get a massive amount of screen time: probably wise, given how comical the drones look as they flap and bob about during Tegan’s rescue attempt. The idea of them – woodlice that would curl around their victims – is interesting, but the costumes look dafter than the Myrka with their flappy little arms (not the last time that happens this season). I’m surprised, given his experience, Bidmead thought his idea would be achievable well. I’m also vaguely baffled why they need human minds to control digging machines when their gravity powers would seem to remove any need to rely on equipment or people. At least the Gravis has a bit of personality – even if he does have the face of a spider baby from A Ghost Story for Christmas: The Ash Tree.

Next episode: Frontios – Part Four