It’s Pertwee’s face in the titles but to all intents and purposes the Master is the lead in this episode. He gets to do all the Doctorish things including, astonishingly, being the first character in the colour era we follow into the TARDIS. He potters round the console, tutting, flicking switches and tinkering in a way we haven’t seen since Troughton. He even gets standard third Doctor dialogue, snapping at the cautious Sir George, ‘Risk the cables, man. Risk everything you’ve got.’ At the cliffhanger it’s the Master who, with no obvious relish, tells the Brigadier if they’re to save the world they’ll have to sacrifice the Doctor and Jo – and waits on the Brigadier’s response before he acts. He’s a villain, but with Delgado and Dicks characterising him, he’s so much more than that.

On the flipside, the script is also playing to Pertwee’s strengths. Someone was taking notice of the way he upped his game when the Doctor has his back to the wall in the Inferno interrogation sequence, and so we get another scene of him strapped to a chair being tortured. Axos’ interest in getting the secret of time travel and its offer to restore the Doctor’s memories add an interesting element to the story, and play into the idea of the Doctor being tempted by what he’s forgotten: a “greed for knowledge” that will come back to haunt him.

Greed is a major theme of the serial. Chinn’s greed has, in a curious way, been helpful because it’s confined the Axon threat to Britain. However, now the UN has got wind of the promise of Axonite, ‘a bait for human greed’, everyone wants a piece. And the motivation for Axos itself is greed: it wants to literally eat the Earth, and then travel through time and space like a malevolent fungus, consuming everything. It’s a notion made clear in the way an Axon walks straight into the nuclear reactor (Michael Ferguson inserts his signature shot of the monster backlit by the sun, as a kind of callback to The Seeds of Death and The Ambassadors of Death) and eats up all its power, while the Master’s plan involves giving Axos indigestion by feeding it all the energy in a single gulp.

There’s also an intriguing scene where the TARDIS seems to turn on the scanner automatically and show the Master the nuclear power relay – prompting him to realise there’s a way to get the Ship working again. It’s as if the TARDIS wants him to restore it. Maybe it’s as bored of exile as the Doctor is, and is even willing to steal another Time Lord to escape…

Next episode: The Claws of Axos – Episode Four