Every time this adventure seems to be about to grind to a halt, John Lucarotti throws in the next stage of the journey. But it’s always one step forward, two steps back. At the end of the previous episode the TARDIS crew looked on the verge of escape, but were dragged back into Marco’s trek. In Mighty Kublai Khan, three of the time travellers finally dare to go to Xanadu (where, disappointingly, no neon lights are shining), but another has to go backwards in order to rescue Ping-Cho, who has decided she doesn’t fancy the idea of marrying a man old enough to be her grandfather.

When Ian gets back to Cheng-Ting, he discovers that the TARDIS has been stolen, this time by a thief who wants to sell it to Tegana. Again, we’re reminded of what’s at stake in a conversation between Ian and Marco: the TARDIS is the way home for both of them. In an attempt to convince Marco to return it to the Doctor, Ian reveals he is from the future. But, in a neat pay-off to Marco’s character development in the previous five episodes, he doesn’t believe Ian. Marco has already been established as a practical man willing to believe the evidence of his own eyes – be that a burning rock (coal), a flying goblet (a Buddhist trick), or Ian’s basic dishonesty (lying about stealing the TARDIS key to protect Ping-Cho). He’s less willing to believe abstract or nebulous ideas like Tegana’s labyrinthine duplicitousness or time travel.

There’s another nice piece of character work when Tegana works out the way to rile Barbara: suggest she’s just Ian’s Yes Woman:

Tegana: How very unusual for you and Ian to disagree.

Barbara: It isn’t unusual at all. We don’t agree about everything.

It’s interesting that contrasts keep being drawn between the two teachers, from Barbara’s readiness to believe in the TARDIS as far back as The Cave of Skulls, to her willingness to side with the Doctor against Ian in The Expedition. It goes a long way to establishing the two characters as equals, with different motivations.

The highlight of the episode is the much-heralded appearance of the Mighty Kublai Khan himself, preceded by a lot of kowtowing. The Doctor, who’s again been pretty much relegated to the background for most of the episode, gets a nice comedy moment when his sore back prevents him from slithering along the ground in supplication. The joke being, the great Khan is as old and short-tempered as the Doctor, suffering from gout and thoroughly decrepit. As the two of them stagger out, arm in arm, to partake of Xanadu’s healing waters, Susan giggles: ‘That’s the mighty Kublai Khan?’. She’s immediately rebuked by Marco, who reminds her the Khan is the world’s greatest administrator: human greatness and human weakness are not exclusive conditions, and great men are men nonetheless. I really like this: debunking eminent personages, Lytton Strachey style, feels absolutely aligned to the early 1960s satire boom that reached its TV peak in 1962-63 with That Was The Week That Was. I’m sure a contemporary adult audience would have enjoyed the idea that throughout history the high and mighty were as fallible as the rest of us.

The episode ends with Ian confronting Tegana. It doesn’t exactly imply this adventure is going to end anytime soon: it’s not as though it’s a shock reveal, or that Ping-Cho didn’t already believe Tegana was a villain, and it feels like a disappointingly repetitive climax to an episode that’s had enough new incident to avoid being just another week of treading water.

Mighty Kublai Khan no longer exists. Not in any of its regenerations. This review is courtesy of the excellent Loose Cannon reconstruction

Next episode: Assassin at Peking