Whittaker and Grover wax lyrical about rolling back time to a golden age, promising that although they’ve been misleading their followers, ‘we’re going to bring the past to them’ even if it means condemning the rest of the country while they pursue their dreams of growing their own food, making their own furniture and bringing it all back how it used to be. Their pernicious nostalgia, a pining to duck the difficult decisions and complexities of modern life in favour of clinging to a rose-tinted perception of an easier, happier past, suggests that the real dinosaurs are these fogeys.

I’m really enjoying the stakes in this story. The conspirators are willing to wipe out the human race to turn back the clock. The reveal that the “colonists'” destination is actually just this planet is brilliantly chilling: ‘Their new world is this one’. I like Sarah’s absolute conviction in her own rightness: she refuses to believe she’s in space, and walks out of an “airlock” to prove it, which is a real power move. She’s very capable: she escapes the bunker, makes it back to UNIT HQ, and blows the conspiracy wide open. Unfortunately, she chooses to tell all to General Finch, and with the horror of a nightmare, finds herself right back where she started. Trust no-one.

Having been framed as the orchestrator of the dinosaur invasion, the Doctor suspects everyone, twigging that Mike Yates is the inside man, and even seeming to have doubts about the Brigadier (surely not that he’s a conspirator, but presumably just that his sense of duty will override his friendship). This leads to another great scene for John Levene (over the last three seasons he’s had many more of them than Richard Franklin). Benton’s loyalty to the Doctor is as unwavering as Jo’s, and he allows himself to be knocked out so the Doctor can get away. With Jo gone, and Mike revealed as a traitor there’s a sense of the UNIT Fam falling apart, an end-of-an-era feel to the story that only works when the audience has had chance to get familiar with these characters.

This is another episode with a lot of lurking about. Paddy Russell’s direction sells it well: the location filming of the manhunt for the Doctor is dynamic, and turning down the studio lighting gives the sets depth and shadow (not always the case with 70s video drama). Only the climax, featuring prehistoric monsters materialising all over a model village, is disappointing.

Next episode: Invasion of the Dinosaurs – Part Six