This one could do with a little bit more incident, but the story is moving along. The major difference from Baker’s collaborations with Martin is the lack of an obvious catchphrase, and the relatively disciplined number of ideas. The three distinct plot strands – the drug smuggling, the Continuous Event Transmuter and the hyperspace collision – are clearly connected, with a mysterious stranger running through all of them hotly pursued by the Doctor.

The CET is essentially the Miniscope from Carnival of Monsters except instead of a carny’s peepshow it’s a big screen TV – one that, in the excellent cliffhanger, the Doctor leaps into as eagerly as he did the Pit. I think kids in the audience would have loved the idea of going into the TV. I like the Doctor’s encounter with an angry passenger (he offers a jelly baby as compensation). I’m also a fan of the lightly sketched intrigue between Tryst, Della and her ‘close friend’ the late lamented Stott, which has all the hallmarks of a key scene in a Miss Marple. It certainly casts some doubt on Della, who is otherwise a bit of a drippy goody-two-shoes. And Captain Rigg’s descent into idiocy after someone (we just see their arm) surreptitiously spikes his tea is nasty. This is shaping up into the show’s best stab at the detective genre since The Robots of Death.

What’s letting it down is the direction. The Mandrels aren’t an impressive monster, but they’re fatally undermined by their introduction, as one waves its arms around through a hole like an over-enthusiastic Z-lister on Celebrity Squares. Shot sensitively, like the one the Doctor encounters in the dimensional interface between the spaceships, they can look pretty good. Green eyes and a huge shape glimpsed through the mist. But mostly Alan Bromly just points the camera at one as it lurches about a brightly-lit corridor. Oh dear.

Next episode: Nightmare of Eden – Part Three