Assassin at Peking (Marco Polo Episode 7)

The one where Tegana's treachery is revealed at last...

Last Christmas I finally learnt how to play backgammon. It only took me four decades to get round to it, but I instantly fell in love with the game, and so it's doubly amusing to see it play a pivotal role in proceedings in Assassin at Peking. And the Doctor's obviously a good player, having already won from the Khan 35 elephants, 4,000 white stallions, 25 tigers, a year's worth of trade from Burma, and one of Buddha's teeth!

But it is the TARDIS that the Doctor really wants to wager for, even though the Khan has yet to see his gift from Marco. Instead, the Doctor is offered the entire island of Sumatra, but eventually manages to persuade Kublai Khan to play for his TARDIS.

Mighty Kublai Khan (Marco Polo Episode 6)

The one where the Doctor's backache earns him an ally...

The telesnap showing Tegana holding Susan at knifepoint is pretty graphic stuff for 5.30pm on a Saturday teatime (I can't imagine they'd contemplate it nowadays!), but it's indicative of just how much Tegana has grown to hate the TARDIS travellers, as he also lunges at the Doctor at one point. What's most intriguing to me though, is something that might only be solved if this episode is ever recovered: when Ian leaves the TARDIS to try and rescue Susan, the familiar hum of the Ship's interior can be heard outside in the courtyard. I guess this means the TARDIS door remains open (the hum stops when the Doctor and Barbara leave the Ship), but it's odd that the production team never use the audible hum whenever the Ship's door is open in other stories.

Although the characters cross a lot of land in Mighty Kublai Khan, it feels a little like writer John Lucarotti is treading water again. The fact Ping-Cho runs away to Cheng-Ting neatly coincides with Ian's quest to recover the stolen TARDIS, while Marco's caravan forges on to Shang-Tu to rendezvous with the Khan.

Rider from Shang-Tu (Marco Polo Episode 5)

The one where Ian reveals his surprising knowledge of burning bamboo...

After struggling with the patchy audio recording at the start of this episode (don't get me wrong, I'm not complaining!), I soon realised that Rider from Shang-Tu is a rollicking good 25 minutes which really gets the serial back on track after something of a lull. We have both action and intrigue, the perfect mix to excite and engage. John Lucarotti's got his mojo back!

It must be said that William Hartnell is really good in this episode. Watching (and listening!) to these early episodes in order has reinforced my opinion that Hartnell is criminally underrated as both a Doctor and an actor. He's searingly good in 100,000 BC, and demonstrates immense gravitas and screen presence in The Brink of Disaster. You can tell he knew what he was doing. However admittedly, sometimes he stumbled over his lines, missed or pre-empted his cues, and some weeks seemed to lack that fire altogether.

The Wall of Lies (Marco Polo Episode 4)

The one where Tegana's scheming turns Marco against our heroes...

The Wall of Lies is the first of 34 episodes of Doctor Who for which there is no episode to watch and no John Cura telesnaps to look at (most of them are Hartnells from Season 3). John Crockett, the director of this episode, did not ask for telesnaps to be taken (they had to be paid for), and so all we have is the audio recorded by David Holman from that magical Saturday teatime back in 1964...

The main feature of this episode is Tegana's scheming, and the effect it has on the dynamic of Marco's travelling caravan. Until now Marco had been a cautious ally, or at least open-minded, but as a result of Tegana's duplicitous lies, by the end of the episode, his "wall of lies" has succeeded in turning Marco against our heroes.

Five Hundred Eyes (Marco Polo Episode 3)

The one with an episode of Jackanory in the middle...

If nothing else, Five Hundred Eyes is educational! The original remit for Doctor Who was for it to be a source of knowledge as well as to entertain, so that younger viewers could learn something as well as be thrilled by the fantasy elements. The historical stories educated the children about history and culture, and the sci-fi serials tended to have more about technology and ideas.

Marco Polo is perhaps one of the richest historicals Doctor Who ever did. John Lucarotti's research is obvious, but the educational element in Five Hundred Eyes isn't exactly delicate. We learn about the Hashashins, Ala-eddin and Hulagu, and also how condensation forms. It's all very interesting, but woven into the script with little subtlety.

The Singing Sands (Marco Polo Episode 2)

The one where the water runs out...

Considering the foul mood the Doctor was in during The Roof of the World, it's amusing to discover that he's been giving Marco an ear-bashing for the last three days. He has had "to endure his insults", he writes in his journal, but to be honest, why is Marco surprised? He plots to steal the Doctor's property for his own personal gain. I don't blame the Doctor for being annoyed.

The Doctor – not seen on screen – also refuses to eat with the others, and declines food when Susan takes it to him. The threat of the loss of his Ship has obviously affected him deeply. The TARDIS is the source of the Doctor's authority, power and freedom, so its loss would utterly destroy him.

The Roof of the World (Marco Polo Episode 1)

The one where the TARDIS's lighting and heating goes on the blink in one of the coldest places on Earth...

The first thing that strikes me about the start of The Roof of the World is just how grumpy the Doctor is! My goodness, he's in a mood! This seems odd seeing as he was in pretty high spirits at the end of The Brink of Disaster after making up with Barbara. But then, maybe this sudden mood swing is understandable: he's having trouble breathing in the thin atmosphere, he's freezing cold and has just discovered that his Ship's broken down (again!). The news that the TARDIS is on the blink would actually be pretty disturbing after what they've just been through, although only the Doctor seems very bothered.

"We're always in trouble, it follows us everywhere!" he blusters, reporting that the lights in the TARDIS have gone out, and the heating's broken too (it's a shame we don't get to see a shadowy TARDIS interior). "Everything's gone to pot!" William Hartnell is a little neurotic in this scene, overplaying the Doctor's anger and frustration a little. "We'll all freeze to death!" he exclaims. Blimey, calm down Doctor!