Viewed as a sci-fi historical, the Time Ring fulfils the same function as the inaccessible TARDIS in those early Hartnell adventures: the Doctor and friends have to go back into the Kaled bunker, whether they like it or not. After all, this is the one time when the Doctor could legitimately walk away, claiming that he took on Time and Time won. Instead, he’s plunged back into the nightmare of Dalek history, forced to relive every encounter so that Davros, turning the tables on the Doctor, can change the future.

This episode is about as dark as Doctor Who gets, featuring an actual holocaust. The Doctor’s look of horror and defeat as he watches the Thals launch their final, murderous attack on the Kaled dome (which, he assumes, has also killed Sarah Jane and Harry) is extraordinary: David Maloney has coaxed superb performances from all the actors. This is pretty much the Doctor at his lowest point since 1969. When friendly, dungaree-clad Thal Bettan asks what he’ll do now he can only say, ‘Start again…’ But there’s no enthusiasm in it, just a sense of getting back on the treadmill. In this moment there’s a hint of Peter Capaldi’s final scenes as the Doctor, worn out by all the death, having to steel himself to carry on.

I love Maloney’s direction here. The first scene fades to black as the Doctor is electrocuted into unconsciousness. So much is played in shadow; whispered, conspiratorial conversations, shot close up, build the paranoia; Nyder’s secret meeting with Gharman is brilliant – the sudden knife twist of Nyder’s betrayal followed by Davros emerging from the dark. As in The Power of the Daleks, the Daleks’ growing strength is indicated by their gradually increasing numbers – one in Part Two, two in the previous episode, three here. And the end of the episode, with the Doctor having to bargain himself against the futures of Harry and Sarah to appease a madman who holds ‘all the torments and agonies ever known’ is thoroughly horrible.

Next episode: Genesis of the Daleks – Part Five