‘The Mysterious Planet’ is a tough story to get a grip on. There’s an ineradicable sense of disappointment hanging round it – as Robert Holmes’ final finished scripts, after an 18 month wait, after all the excitement of the hiatus fans expected more. And they got what’s been described as ‘mundane’, ‘not terribly involving’ and ‘a mess’. And it’s true that there are maybe too many knowing nods towards criticisms of the previous season – “Why do I have to sit here watching Peri get upset?”, “a certain amount of graphic detail is unavoidable”; “You drain my energy resources with your constant infantile bickering” – without really necessarily just fixing them and moving on.

But for all that, it’s still a Robert Holmes script, and still has a certain power to it. Particularly the climax, in court, when, in between insulting the Doctor’s immaturity, the Valeyard finally gets to the nub of his argument:

“Lives were lost because of your meddling”.

And that’s the unanswerable question, isn’t it: lives are lost because of the Doctor’s meddling. The Time Meddler might as well be the show’s title: it’s just what he does. And he gets people killed. Yes, of course, in the service of the greater good, even to save the universe. But even so, people die.

“If you hadn’t come here, on a whim, would anyone here have died?” asks Joan Redfern. “How many more? Just think: how many have died in your name?” sneers Davros. And the tenth Doctor never has an answer. The Valeyard suggests the Doctor is a destructive force, that it would be better for him never to have left Gallifrey. And here, we get to the heart of the trial: is it better for Doctor Who to continue, or for it to die?

It’s hard to credit people who suggest the courtroom scenes are an irrelevant distraction – to Holmes, they’re the only point. The adventure on Ravolox is deliberately generic, an opportunity for the Valeyard to question the basic premise of the series by asking the jury (that’s us) to watch a standard Doctor Who adventure through his eyes.

And in the climax, Holmes focuses on that message. The climax involves the Doctor appealing to the humanity in Drathro, begging the robot let him save the lives of all the organic life on Ravolox. And let’s be clear: Drathro isn’t even threatening to kill the people of Ravolox, he’s just not willing to allow the Doctor to act to save them. Drathro’s inaction in the face of genocide is therefore implicitly compared to the Time Lords’ non-interference. In an ivory tower, the rest of the universe can go hang, so long as the gods don’t actually have to get their hands dirty. However, the Doctor refuses to remain detached, to just leave in the TARDIS. He argues ethics with the robot, he talks about his belief that every life, no matter how small, has value and purpose. In the end, The War Games defence still stands: the Doctor might get involved, but it’s better than doing nothing.

After that, the actual solution – pressing a few buttons then running away from the explosion – is oddly prescient of the Russell T Davies series where the plot was always subordinate to characterisation and moral dilemma. The Trial of a Time Lord is very much about the character of the Doctor. On this basis, ‘The Mysterious Planet’ is a purposely disposable piece of fluff, but The Trial of a Time Lord, at least as written by Holmes, is almost gripping. But what a shame they couldn’t jump directly to Part Thirteen.