‘Are you really offering this inconsequential silliness?’ Philip Martin probably seemed a safe bet for the Trial scenario: after all, Vengeance on Varos notably featured characters watching and commenting on the action unfolding on TV. And with the promise that this story ‘in which he was engaged when removed from time and brought to this court’ provides the immediate context for the trial there’s a real potential for Martin to build on his earlier ideas and do something truly different.

So it’s a bit perplexing that this is where the court room scenes start to feel like they’re getting in the way. The Thoros Beta story is a lot more interesting than the Valeyard and Doctor settling into trading insults. It draws on some of the ideas in Vengeance on Varos – experimentation on live subjects; bodily transformations; capitalist exploitation; Sil – and gives them a greater sense of purpose. Crozier’s Dr Moreau experiments are in the interests of saving the life of the planet’s ruler, Lord Kiv (a very dry Christopher Ryan) rather than just morbid curiosity. We’re quickly introduced to some of his earlier attempts: the Raak and the Lukoser, and both are painted as victims of the real monster. In a series where deformity generally equates to villainy, this is a nice touch – and reinforced by Sil’s almost unique disinterest in the ‘revoltingly ugly’ Peri.

Martin’s script also wins in its approach to the Doctor and Peri. The Doctor is already behaving like his next incarnation: deliberately going to Thoros Beta to put a stop to their manipulations, “forgetting” to tell Peri it’s the home planet of Sil and ignoring her objections. I sense this is what the sixth Doctor ought to have been like all along – different from the Davison version not because he’s less compassionate, but because he’s more of an active interventionist, seeking out evil rather than being disappointed to find it, and not letting his companion in on the whole truth.

Ron Jones’ final Doctor Who directing gig is largely his best effort yet. The Raak, not an especially convincing monster, is revealed only in flashes of detail – a huge claw, a glimpse of fangs. The cave interiors look gloomy; the planet’s surface is neon azure, pink and blue, which is faintly sickly but much more fun than the usual sand pit. He also gets some good performance, like Baker playing the Doctor’s disturbed “what did I do?” reaction to the Valeyard’s promise of ‘clearer examples of your guilt.’

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