Russell T Davies channels Black Mirror in a story of AI, shallow social media, and posh white supremacy. But, naturally, with added slug monsters

“Oh my hopscotch!”, as Lindy Pepper-Bean might say. The on-screen lead for much of this episode, Callie Cooke, is surely one of the most dislikeable human characters Doctor Who has ever produced. She is vain, shallow, self-absorbed and manipulative, and not afraid to cause her idol, Ricky September (Tom Rhys Harries), to die, and then lie about it. Regardless of the presence of the slug monsters, she is undoubtedly the villain of the piece.

It was strikingly stylised, and unusual to see an episode of Doctor Who mostly colour-graded to be pastel pinks and blues until the final subterranean act. The obvious target was the vacuousness of much of social media, but writer Russell T Davies struck out at wider themes, including the idea that AI might come to hate humans, and the arrogant privilege that comes with being, as Ruby Sunday put it, the “rich kids”. The inhabitants of Finetime had been sent off to a posh offworld boarding school and apprentice scheme for the wealthy and conventionally attractive, where they mostly partied. “Some of us get eaten” was both factually true for the story, and a bleakly observant pun for the viewer. Some people do get Eton.

Millie Gibson takes centre stage as she lives out a life that is packed with the supernatural – but without the Doctor. It’s a stone-cold classic … until its final moments

After the suspense of last week’s Boom, the new Doctor Who season cranked up to full-on horror in 73 Yards, with an episode destined to be remembered as one of the all-time great companion performances.

Once the Doctor vanishes, it is left to Millie Gibson as Ruby Sunday to unravel the mystery that then stretches through the whole of her life, morphing from creeping dread in rural Wales to a political thriller split between London and Cardiff. Aneurin Barnard cut an impressive figure as the paranoid and controlling populist politician Roger ap Gwilliam, somewhat in the mould of Emma Thompson’s Vivienne Rook in Russell T Davies’ Years and Years.

Steven Moffat’s return to Doctor Who has alien planets, murderous AI – and Ncuti Gatwa trapped in an incredibly tense race against time

After two episodes, where Doctor Who seemed determined to greet any potential new Disney viewers with everything that could be fun, camp and ridiculous about the show, this was a darker turn from the pen of former showrunner Steven Moffat.

The conceit that the Doctor (Ncuti Gatwa) could not move for nearly the whole episode, and instead had to rely on Ruby Sunday (Millie Gibson) to get him out of a fix, dialled up the tension and gave both actors a chance to deepen their characterisations. Ruby is clearly prepared to take risks, and this Doctor is more vulnerable and emotional than some previous incarnations. You could imagine Peter Capaldi trying to sarcasm his way out of being stuck on a landmine, rather than being forced to sing a haunting soldier’s lament to calm the nerves.