‘The Doctor is on trial for his life, yet in his defence he presents us with a situation in which he is deliberately flouting accepted authority.’ This is all lively enough, but it introduces what I’ve always felt is a flaw with the story. If this were a true Agatha Christie pastiche then the focus would be on the murderer and the investigation. But as Doctor Who needs monsters, so here the focus begins to shift to the Vervoids and their plans for the crew, and for Earth. Suddenly, it’s no longer a neat murder mystery but a story about obscene vegetable matter exterminating humankind.

The Robots of Death managed to include monsters by having them as the murder weapon, under the control of the killer. By giving the Vervoids agency and sentience I think this undermines the purity of the detective story, and also the Doctor’s defence. He does, after all, actually commit genocide: ‘We are unique, the only members of the Vervoid species. If he succeeds in eliminating us, Vervoids will cease to exist.’

“Rhubarb, rhubarb, rhubarb”

On the other hand, at least the Vervoids give a bit of a boost to an episode that’s otherwise a bit slow: the Doctor gets hauled in front of the Commodore, again. Bruchner snaps at Lasky, again. Lasky goes to the gym, again (seriously, it’s like she’s permanently getting in and out of that lilac velour tracksuit – you could probably power a Dalek off the static). I quite like the attempted murder of Mel, and there’s a token attempt to connect the Hyperion III story to the Trial conspiracy plot by means of a “faked” scene of the Doctor giving 40 whacks to the communications equipment. The Vervoided Ruth is quite Seeds of Doom, even if it’s quickly moved past. The end, as Bruchner snaps and decides he’d rather plunge the spaceship into the Black Hole of Tartarus than take the Vervoids to Earth, is great.

Next episode: The Trial of a Time Lord – Part Twelve