This must be one of the thinnest scripts the series has had to date: whole stretches involve the Doctor driving round deserted London and lurking first in an abandoned tube station, and then an underground bunker, all in the name of playing catchup with Sarah Jane – who already discovered all of this last week. As such, it’s fine, but does feel like it’s just noodling on things we already know (for example, Mike Yates complaining again that he never agreed to murder the Doctor), and finishing with the implausible idea that the Doctor could be framed as the mastermind behind the Dinosaur invasion.

The most interesting development in the previous episode was the idea that Sarah had been on board a spaceship for three months. Even in a serial that heavily foregrounds time travel, this seems unlikely, as things haven’t moved on at all for the Doctor and Brigadier. Still, Sarah’s presence in the midst of a very middle class community of The Good Life types full of good intentions, remains intriguing, especially when it turns out that Ruth (‘Allo ‘Allo‘s Carmen Silvera) is as psychopathic as we always suspected Tom Good might be. If Sarah refuses to be euphemistically ‘re-educated’ (that is, brainwashed) to go along with the community’s back to the soil ideas, she’ll be eliminated. This plot thread is reminiscent of the terribly nice people Salamander secreted underground in The Enemy of the World, but Ruth’s (formerly Lady Cullingford) bland ruthlessness and willingness to cull discontents adds a disturbing and surely intentional angle of bourgeoise hypocrisy to Communist Malcolm Hulke’s script.

The Doctor, meanwhile, is more interested in trying out his new car. The Whomobile is a bit stupid and gimmicky – it needs something as charming as K9 to get away with this kind of obvious merchandise opportunity. The Whomobile is more of a Kamelion. Still, it’s presumably keeping Pertwee entertained in a particularly thin week for him. The only other amusement he gets is battling off a pterodactyl with a mop (putting to good use the moves he learned while he was living as a Welsh cleaning lady), and then later getting into a broom cupboard with the Brigadier.

Next episode: Invasion of the Dinosaurs – Part Five