‘So that was the year of the slow invasion, when the Earth got cubed, and the Doctor came to stay.’ In a surprise twist, this year’s Gareth Roberts script is written by Chris Chibnall. As Craig is otherwise engaged as a contestant on The Apprentice, it falls to Amy and Rory to play hosts as the Doctor crashes their ‘beautiful, messy lives’ to investigate the mysterious cubes that have appeared from nowhere, all the way round the world. And there’s another surprise – the Brigadier might have died, but his daughter Kate from the Ian Levine spin-off Downtime has taken charge of UNIT.

For an episode steeped in the fandom of the 1980s (Chibnall and Levine, I suspect, were on the same page around 1987), this is pretty good. The cubes are a striking image, and their inscrutable just-there-ness for the bulk of the episode makes them much more sinister than a shedload of Cybermen. It allows Chibnall time to focus on the Doctor’s reaction to real life – not the comic attempts to fit in from The Lodger, but the challenge of ‘living a life day after day. The one adventure I can never have’ because he hates it. And it lets him explore Amy and Rory’s dilemma – embrace that human life or abandon it for life and death in time and space. Brian, back from Dinosaurs on a Spaceship, helps them make the decision – so this becomes the goodbye to them he’ll never get again.

All of this is Chibnall’s best character work for the show, and The Power of Three succeeds when it foregrounds the human drama. There are some brilliantly observed moments, like Brian’s perfect spelling out of U.N.I.T., and his concern for his son and daughter-in-law – you can see, in this older man, the roots of Graham O’Brien, and I suspect between this and Dinosaurs on a Spaceship we get our most clear indication of Chibnall’s future approach to the show.

Which includes some of the downsides. Because the mystery, as so often the case, is much more interesting than the answer – the cubes are the vessels of an ancient Time Lord legend called the Shakri, hinting at Chibnall’s interest in exploring Time Lord lore and mythology. They’re meant, in an unnecessarily convoluted way, to kill off humankind before it can infest the universe. Once The Power of Three shifts focus to the Shakri spaceship above the Earth, it falls to bits (it doesn’t help that the portal to a spaceship filled with comatose victims and a hologram, and an urgent need for CPR is very close to the denouement of The Curse of the Black Spot). Steven Berkoff’s performance, staring into the distance as he waffles nonsense, doesn’t help to sell it. The journey was better than the destination. But, this time, the journey was good enough to justify itself.

Next Time: The Angels Take Manhattan