Fittingly, this episode focuses on the power of myth and the lasting influence of heroes from the past. Omega is a kind of Gallifreyan Moses, the ‘solar engineer’ (I love the idea of someone who can create suns, no wonder he has a God complex) whose sacrifice gave his ‘brother Time Lords’ (no mention of Tecteun or the Shobogans here) their time and space travel. But while he’s been revered and remembered by Gallifrey, his continued existence, as a force of will, has left him jealous and resentful at his imagined betrayal and abandonment. I like the idea, the sense that the past can come back to haunt the present, especially in an anniversary story. In a sense, Omega is fulfilling the same role as the War Doctor in The Day of the Doctor: the guilty secret underpinning the show’s current incarnation. Only by acknowledging the past can we move on from it.

In practice, it’s not entirely successful. Omega’s immense power amounts to conjuring up a chair and pitting the third Doctor in a slow-motion wrestling match against a troll. But the bathos of some of the execution is made up for in the majesty of some of the ideas: Omega’s ability to sustain himself and his entire world through willpower, and some of the revelations about Time Lord history – revelations that must have been as stunning in 1973 as the Timeless Child was in 2020 – are pretty strong. And partly it’s the reactions of Pertwee and Troughton that help to sell Omega’s greatness: they play the Doctor’s awe brilliantly, whispering like schoolchildren when his back is turned, looking suitably chastised when Omega commands the the third Doctor to be silent.

The regulars’ performances are great all round, actually. If you can accept the Brigadier is now a comedy buffoon, Nick Courtney’s shock at arriving on an alien planet and trying to process this news is very funny. Troughton and Levene continue to be a hugely effective pairing as they encounter the Gell Guards (eliciting Troughton’s immortal ‘Oh my giddy aunt!). Once you know that behind the scenes Pertwee and Troughton clashed over their different approaches to learning lines (Pertwee on script, Troughton approximating) it’s also extremely amusing to see Pertwee assiduously listening for his cues when he and Troughton are explaining the technobabble to Jo, Dr Tyler and Benton. The two of them, as you might expect, are hugely entertaining together: the punchline to Episode One’s tossed coin joke (this time the resigned third Doctor catches it in mid air) is beautifully done. While this isn’t perfect, it’s as charming as the series gets. As is Hartnell’s grumpy response to being dispatched into the black hole: ‘Well, better than being stuck here, I suppose.’

Next episode: The Three Doctors – Episode Four