There’s a school of thought that whilst Inside the Spaceship, the original TARDIS crew erupts into conflict and then everyone makes up, settling into a comfortable team. This is allegedly the point where, after 13 weeks of experimentation, the show finds its standard shape and settles into a pattern. From this point of view, Marco Polo is a standard historical adventure, albeit the first and a bit grander than most. But this neglects how wildly experimental it is and that it too plays a part in helping the show find its groove. The Keys of Marinus feels much more like the typical sort of story Doctor Who will settle into. Marco Polo is, aptly enough, exploratory.

Its original name was A Journey to Cathay and that suits it far better. Because this is a literal journey across 13th century China and a metaphoric journey for our travellers and chief protagonist Marco Polo (Mark Eden). Uniquely, this is a story which takes months to unfold; the televised sections are just the edited highlights, linked by narrative excerpts from Polo’s diary. This makes it Doctor Who’s only road trip story, and such stories are always about charting the change in characters as they progress along their journey.

What did this story’s viewers back in 1964 think of being dragged along this trek for nearly two months with our heroes? They would surely have noticed, even in its weekly episodic formats, a plot which is the slowest of slow burns. Writer John Lucarotti gently doles out incident after incident for seven weeks, fuelled by two major plot strands which sustain the dramatic tension. The first is the struggle for possession of the TARDIS, played out between our heroes and Polo. The second is the treachery of Mongol warlord Tegana (Derryn Nesbitt) which the TARDIS crew are convinced of, but Polo is not.

The first plot strand prompts multiple attempts by the Doctor (a waspish William Hartnell) and his friends to regain the TARDIS by fair means or foul. Each gambit gets frustratingly closer than the last, but each inevitably fails and with each failure, those earliest episodic viewers must have realised they had at least one more week of Chinese antics left before the series got back to bug eyed monsters. The second plot strand generates various attempts by Tegana to disrupt Polo’s caravan. All his ploys – your draining of water gourds, your facilitation of bandit attacks and so on – are shared with the audience before he attempts them, keeping us one step ahead of both Polo and our TARDIS chums.

The incidents within these two plot strands repeat and overlap each other through the seven episodes. In fact, the whole story is a bit like listening to two vinyl records simultaneously, both of them stuck on a groove. Our friends plan an escape, make their attempt, they fail and face the consequences. Tegana hatches a plot, executes it and is foiled. Repeat and repeat until we reach Peking.

And in between these two narrative drivers, there are other road trip hijinks to fit in: getting lost in a sandstorm, a runaway girl, an attempt to steal the Ship. There’s even time for a poetry recital in the middle of it. This story is in no hurry.

Which is good, because it’s also trying to teach you stuff. Not an episode goes by without an attempt to educate as well as entertain, on subjects as diverse as the boiling temperature of water at heights, how condensation works, the speed of messengers on horseback and the explosive potential of bamboo. Never has the show’s original instructive premise been taken so seriously.

This what I mean by the story being experimental: it’s working out what a Doctor Who historical should be. Should there be a problem for our TARDIS crew to solve? Or should they simply be caught up in events, struggling to get back to the Ship? Should each episode be scattered through with educational nuggets? What’s the mix between drama and comedy? It’s notable that they never again tried another 7 episode historical; after Season 1, all historicals are restricted to 4 parts. Marco Polo is R&D for all the other historicals. Even the 21st century’s celebrity historicals take their lead from this one.

There’s also something experimental in its exploration of morals and its ability to tie them to its plot. The recovery of the TARDIS is a case in point. Polo confiscates the TARDIS because he wants to give it to Kublai Khan (Martin Miller, one of many actors in yellowface, unfortunately). The Doctor makes various attempts to steal it back… but the message here is he can’t win through trickery. Even when he’s an odds on favourite to win it back from the Khan in a game of backgammon, he loses. He doesn’t regain the TARDIS until Polo gives it back to him… and that act is the culmination of a corresponding moral journey for Polo.

It takes seven episodes for Polo to realise the truth of things he’s been struggling with since he met the travellers on the roof of the world. Tegana is up to no good, as our heroes have been telling him. And the TARDIS was not his to take in the first place. To bring the story to its end, to complete is own personal journey, he has to recognise and defeat his enemy but also do the right thing and give back the Ship. True, it’s kind of arbitrary that it takes seven episodes to make it happen. It could have taken four or six or ten, but that’s the saga format for you. It can take as long as you want to reach a destination.

But now that I think of it… wouldn’t it have been more fun if Marco Polo had ditched its pretentions to moral and educational instruction? It could be more like a road trip movie – a kind of Doctor Who version of The Hangover? The Doctor, Ian (William Russell) and Polo, could go out on the tear and wake up to a tiger in their caravan. Susan (Carole Ann Ford) and Ping Cho (Zienia Merton) could steal a couple of fast horses and rack up some bills on the Khan’s expense account. Barbara (Jacqueline Hill) could wake up married to that handsome Ling Tau (Paul Carson). Now those seven episodes would fly past in a blur! And as the Ship departs our heroes could all wearily agree that what happens in Cathay, stays in Cathay.

LINK TO The Magician’s Apprentice/The Witch’s Apprentice: the Doctor is separated from the TARDIS in both.

NEXT TIME… Inquests bore me. But luckily it’s Time and the Rani.