This is easily the best episode of the serial so far. Possibly that’s because it’s the only one still to exist, and we can therefore see Derek Martinus’ direction makes the most of the rather stretched material – for example, in Maaga’s straight-to-camera speech; the gruesome flashback to the first contact between Rills and Drahvins, and the cross-fades as Steven’s air runs out. However, there’s also a bit more substance to this episode than the last two weeks.

Partly that’s because the introduction of the Rills adds a much more interesting species of alien beings than the Drahvins. Barring Maaga, they are all one note, tiresome conversationalists. Whereas the Rills, with their plummy voices and rather dry sense of humour (I love the mild ticking off they give the Doctor first for shouting, and then for fiddling with their ammonia machine), are great. There’s a wonderful moment when a Chumbley apparently analyses Vicki’s speech, processes it, and then begins talking in English. We don’t glimpse a lot of them, but they’re clearly stranger looking than most Doctor Who aliens as well.

On the other side, Stephanie Bidmead continues to be the most impressive performer in the episodes. Her ecstasy as she imagines the death of the planet, and later as she tortures Steven, is utterly nasty. And like Martinus, she makes the most of some quite dull dialogue about the value of friendship.

The Doctor and Vicki get the lion’s share of material as they negotiate with the Rills. Once it becomes clear that Maaga is torturing Steven, they both make off for the Drahvin spaceship, and the moment where the Doctor orders the Chumblies to war is fun. Vicki is even better, pretending to have captured the Chumblies as the pretext to wrestle a gun from a patrolling Drahvin soldier before marching her off at gunpoint. She’s magnificent.

William Emms’s script has a couple of vaguely interesting juxtapositions. The Drahvin’s are removing Steven’s atmosphere, just as the Doctor plans to remove the Rills’. And the Doctor says he is happy to help the Rills as they are helping him – in contrast to Maaga’s selfish desire to steal the Rill spacecraft and leave the other people to die when the planet explodes. But while Air Lock has more incident than the previous two instalments, this is still probably the most condescendingly ‘for the kids’ story to date with all of these points made blatantly rather than in subtext, and with no subtlety. As such, it’s not disastrous but it’s a long way from the sophistication of the previous serial.

 

Next episode: The Exploding Planet