It’s been a while since we’ve had a baddie go certifiably nuts, so it’s quite fun when Paul Whitsun-Jones really goes for it with the Marshal’s flip into fruit loops madness, staring wide-eyed at his model of Solos as he plots his new empire. He’s got competition though from possibly the gayest moment in the series to date as Ky transforms into a sparkling rainbow fairy and floats about beatifically. In between these two transcendent performances we get a courtroom scene (always a good move) complete with surprise witnesses and some rhubarbing administrators from Earth.

There’s a lot going on in this episode: Cotton, astonishingly, gets made acting Marshal; the Mutts make a move on Skybase, with one of them wandering cutely into the courtroom to wave its pincers plaintively, and Jaeger is presumably killed when his genocide machine explodes in his face. It’s not exactly carefully crafted prestige drama, but it’s cracking Saturday night family TV. And some of the one liners (the Doctor is ‘qualified in practically everything’) are fab.

It all ends, like The Curse of Peladon, with a comedy sequence for Jo and the Doctor (he claims she’s feeling faint, much to her outrage), an excruciating joke about a broom cupboard, and a repeat of Amazonia’s ‘Doctor who?’ line suggesting that they’re really trying to make this a running gag. Of course, none of it’s as good as The Curse of Peladon. At times, the serial’s felt stretched very thin across six episodes, and the gap in quality between the film and video sequences has rarely felt starker.

However, the flipside is this is more imaginative and creatively ambitious than anything since The Claws of Axos, which means even if it’s a failure it’s an interesting one. The idea of an entire planetary life cycle is one the show returns to in various forms in the next era, often more effectively, but rarely with such wide-eyed enthusiasm. And if the Doctor’s musings about anti-matter prefigure The Three Doctors, the idea of a crystal in a radioactive cave guarded by insects that triggers a roll-back-and-mix regeneration is almost a blatant foreshadow of Pertwee’s final story. It’s hardly ripe for re-evaluation, but this is not the disaster it’s painted as.

Next episode: The Time Monster