‘The worse it gets the more I love it.’ This one almost feels like it was written as a counterpoint to Midnight. That went dark, with the Doctor failing to hold together a small group of humans stuck on a stranded bus: he even makes reference to it: ‘humans on buses, always blaming me.’ By contrast, this could be called Midday, and not just because it’s set in the blazing dunes of Dubai. Other than the unnamed bus driver, who gets croaked early on to establish the danger of trying to pass through the wormhole unshielded, all the passengers live because they work together, don’t turn on each other, and trust the Doctor. After the darkness of the back half of Series Four, this looks like a return to bright, light comedy.

But this is deceptive. This is, after all, a planet of the dead, where an entire civilisation has been reduced to dust; where the Doctor’s would-be companion is a classist adrenalin junkie with a massive sense of entitlement, and which finishes with a premonition of the Doctor’s impending doom. It’s not exactly unambiguously joyous. Lady Christina is symptomatic of this.On the one hand she seems like an ideal partner in crime for the Doctor: she’s smart, resourceful, brave and enjoys a nice repartee with him. She even gets an introduction straight out of the Cartmel Masterplan, cat-burgling a swanky museum.

On the other hand, she abandons her previous, literal partner in crime to the police; she’s a snob (‘The aristocracy survives for a reason’) who sneers at Carmen’s poverty (‘You don’t look like millionaires’), and she’s no Robin Hood: ‘Daddy lost everything. Invested his fortune in the Icelandic banks.’ She’s superficially charming and fun, but, like San Helios, there’s something very nasty mixed in with the sun and sand. Still, she’s the only “specials year” one-shot you could imagine working as an actual companion: if this had been the opener to Tennant’s fourth series I expect her arc might have been about learning humility.

Between a switch to HD, location filming in Dubai, Murray Gold doing his best John Williams impression, Michelle Ryan excelling as a one-shot companion, Lee Evans playing a proto-Osgood (UNIT scientific advisor who’s a Doctor Who fan) and the presence of future movie star Daniel Kaluuya, this mostly looks spectacular and expensive. A couple of things undermine it. Some of the CGI (particularly the flying bus) doesn’t quite hold up, and the Tritovores are particularly rubbish. At least the latter is a joke: they’re introduced exactly like the Racnoss Empress, via a chitinous claw tapping at a screen, but instead of an enormous spider we get a fly in a boiler suit.

As a gap-year Easter Special, to keep up the show’s profile between Christmas Specials, this is clearly a success, playing like an extended RTD series opener and the last “business as usual” Tennant episode before his departure overshadows everything. There’s not much more to it than that, but sometimes there doesn’t need to be. Even the title seems consciously generic. This fulfils a similar function for the 10th Doctor as Invasion of the Dinosaurs did for Pertwee, or The Smugglers for Hartnell, a final look at what we’ve had before the end.

Dr Who will return in The Wedding of Sarah Jane Smith

Next Time: Children of Earth