After two months’ build-up, the climax delivers despite a clunky fight sequence and everyone seeming a bit less on top of their lines than they have been until now. The warmonger aliens are defeated in a fairly conventional way – having tricked them, and lured away most of their guards, the Doctor and the resistance are able to defeat the remaining skeleton staff in central control and bring an end to the war games. But the real issue is the Doctor’s inability to follow through on his promise to the resistance. With the SIDRATs running out of power (the episode’s one weak contrivance) and the TARDIS un-steerable, the only way to put things right is to call in the Time Lords.

What follows is essentially a repeat of the War Lord’s introduction, but on a more majestic scale. Just as the War Lord’s existence was trailed and his credentials established by the fear he inspired in his subordinates, so the Time Lords, having been mentioned in passing a couple of times, now become a real and present danger. The War Chief is terrified: ‘Doctor, you mustn’t call them in or it will be the end of us. They’ll show no mercy.’ The War Lord is resigned to his fate: ‘When the Time Lords get him, he’ll wish you had killed him.’ And the Doctor is so desperate to get away before they arrive that he stares down Villar, and tries to abandon Jamie and Zoe.

‘They’re coming,’ says a cowed War Lord, like he’s in The Iron Legion. Their arrival, with thunderous organ music, our friend Carstairs fading out of existence, and time slowing down around the fleeing Doctor, pulls out the stops to make a the moment feel as important as the writers think it is. Short of the Daleks turning out to have been behind the war games, it’s hard to think how this could be any more epic on a BBC budget. It’s certainly the single most impressive cliffhanger since The Tenth Planet 4’s.

The script definitely gives Troughton’s Doctor a better send off than Hartnell. He’s given some great material at the top of the episode, a wolfish grin on his face as he unpicks the War Chief’s eagerness to make an ally of him. He plays a dangerous game of who’ll blink first with the War Lord. He fools the War Chief, leads the attack on the control room, and when it becomes clear he has no other choice, he willingly and uncomplainingly risks his existence to save the kidnapped humans.

The Doctor’s stoicism compares well to the War Chief’s self-serving attitude. A vicious liar to the last, he takes his revenge on the Security Chief before trying to steal a SIDRAT and finally running out of clever lies when he’s cornered by the War Lord. His execution, shot repeatedly, at close range, by all the remaining guards, is peculiarly horrible, as is the shot of his twisted, sightless corpse.

Next episode: The War Games – Episode Ten