The problems with Episode Five are that once the Doctor has convinced Earth and Draconia that the Master is trying to tip them, Blofeld style, into war there’s nowhere for the story to go until the showdown. If anything, this week the issue is even more pronounced, with about 15 minutes of pure vamping as the Doctor does an agonisingly slow space walk to repair General Williams’ ship, while Jo stages a prison break and sends a message to warn the galaxy only for the Master to reveal he was pranking her. When Hulke has to resort to the Ogron Eater, a monster that looks far more fearsome as a Lovecraftian mural than a billowing duvet on location, just to keep things going another couple of minutes it’s a bit heart sinking.

Still, when it comes the reveal of the Master’s allies is well handled, and it’s nice that Delgado gets to appear alongside the show’s other big bad in his final episode, eyeball to eyestalk with a Supreme Dalek, even mocking them (once they’re out of earshot): ‘Do not fail the Daleks indeed!’ This is skilfully set up, with the Master warning the Ogrons ‘ They are coming’, and the Doctor having a premonition of their imminent arrival. The big moment, like all the film sequences in the serial, is a lot better directed than the studio work. Paul Bernard has Delgado loom in silhouette on top of a ridge above the pinned-down Human/Draconian expedition, with the Daleks appearing all around them.

Sadly, once they get to studio, the Daleks are as static as in Day of the Daleks, with similarly lifeless voices, proving that Bernard just doesn’t know how to use them, or that the production office has forgotten the twitching, shrieking monsters of the 1960s. And having turned up, they just leave. The subsequent sequence, of the Doctor being shot in a scuffle while the Master makes a break for it, is weak, and robs Delgado, who has been as great as ever in this story (his quiet explanation of his plans to Jo is marvellous) of a grand final exit. 

Possibly the worst thing about Frontier in Space is that the Earth/Draconia story fizzles out completely once the Daleks turn up. The characters in this story just wander off like the end of Shakespeare’s 3 Henry VI, once Richard III has taken centre stage. Madam President is left, head in hands, as a right wing American firebrand rants on the TV (surprisingly topical); the Draconian Prince dashes off while delivering his last line over his shoulder. We’re left to assume they get away and stop the war, because the Doctor now has bigger fish to fry. 

Still, if the ending doesn’t quite work, the serial as a whole is shockingly under-rated. With four planets, four different monsters (plus cameos from the Drashigs, Solonian Mutts and Sea Devils), the Master in league with the Daleks, and the Doctor forced to summon the Time Lords for their help, this is the biggest Doctor Who story since The War Games. It’s also Katy Manning’s best serial to date, as she holds up half the plot, resisting both hypnosis and mind control by the Master, and showing enough quick thinking to steal the fear device and help to save the day. It’s Malcolm Hulke’s best work since Doctor Who and the Silurians, and continues the 10th anniversary seasons deft blend of celebratory nostalgia and event stories with something the series hasn’t really tried properly before. It’s great.

Next episode: Planet of the Daleks