Is it just me or does the Sandminer look like the Thundercats’ Lair? This is a design masterpiece, an entire world imagined around the same aesthetic, from costumes through the the robot masks and the furnishings. Even the corridors, which could easily have been bog standard white moulded flats, look like a high-end, sterile spa. Everything from the witty script out speaks to a decadent civilisation built around a dependence on robots, where beauty and prosperity and one’s position in the social hierarchy are all that anyone really has to think about.

It’s the perfect backdrop for a 1970s Death on the Nile in space: a confined location with sumptuous sets, seething passions and dirty secrets. All that’s missing is the all-star cast: David Niven as the laconic Poul, dripping with mordant humour. Diana Rigg as the sarcastic Toos. Olivia Hussey as the rich socialite Zilda etc. This pulls no punches, with murder by strangulation and burial alive, and a killer with a sinister calling card – the corpse marker left at the scene of the crime. Because most of the audience will get the Agatha Christie allusions, it leaves Boucher free to thread in some proper SF ideas, laws of robotics and so on. It’s beautifully done.

It helps that while the Sandminer crew squabble among themselves, the Doctor and Leela spend the episode with only each other (and a couple of robots) to talk to. This helps cement the relationship they started to build in the previous serial. This is fun: the Doctor becoming a wise old mentor, Leela surprisingly able to speak for the audience given she’s an extra-terrestrial savage, when she challenges the Doctor’s silliness and asks for some straight explanations.

This is prompted by the Doctor’s attempt to explain how the TARDIS is bigger on the inside. After The Masque of Mandragora explained its translation gifts and The Deadly Assassin blew the lid on the Time Lords, there seems to be an emerging effort to explore and explain some of the show’s mysteries. I’m not sure I entirely like this: it’s the kind of introspective approach that ultimately leads to explaining (several times) who the Doctor is. I prefer the mystery myself.

Next episode: The Robots of Death – Part Two