‘Sleep no more, my warriors, sleep no more.’ The early rumours were that Gatiss was going to write a third Peladon story as a Brexit parable. What we get barely flirts with either idea – just Alpha Centauri’s brief cameo and ‘Mars stands alone’. Instead, it’s a British Empire in Space fantasy which plays to golden age sci-fi ideas, and imagery like the brass spacesuits.

Which is a bit of a shame – not because I particularly think we need a Pelxit story, but at least it would have given some shape and distinction to what’s otherwise a re-tread of themes already explored in Cold War, of the importance of giving peace a chance, the danger of chauvinism, over-ambitious second-in-commands and the Ice Warriors’ disproportionate response to acts of violence. Having covered this four years ago there’s little to add here. It’s in a Martian lava tube instead of a Soviet submarine; the main Ice Warrior aggressor is female (with a nice iteration of the old Alan Bennion Ice Lord costume, proving after the Daleks these look the best reimagined classic monsters); the TARDIS relocates itself back to the university rather than the South Pole.

I wish Gatiss hadn’t hewn so closely to the New Adventures’ reinvention of the Ice Warriors as crocodile Klingons. We already have the Sontarans for the whole war and honour thing (and Cybermen for stomping noisily). Gatiss even references an earlier concept of the Martians as star Vikings, raiding and plundering like Slaar, but gradually becoming the civilised settlers of The Curse of Peladon. Instead, the new series risks turning the Ice Warriors into another group of Silurians, one-trick ponies retelling the same story every time they turn up.

But this is criticising Empress of Mars for not being a different story. I like what we get, it’s more fun than Cold War, the British Redcoats versus green Martians looks fantastic. Capaldi is in his final flowering, a powder puff of hair around a wildly grinning face; leaping to action when Bill is threatened and playing along with her previously unmentioned fascination with old movies. The baddies are straightforwardly hissable; the heroes are genuinely heroic. The call-back to Tooth and Claw is cute.

Next Time: The Eaters of Light