The search for the final micro-key takes place over the course of the next episode and a half (this extra time allows for a slightly more involved plot). We’ve reached the city of Millenius and Ian finds himself accused both of murder and the theft of the micro-key. And here, the accused is guilty until found innocent.

Hartnell’s back from his holidays! It’s lovely to see the Doctor again and he turns up at just the right time since he’s the ideal person to speak for Ian at the tribunal. The Doctor’s in his element here. “My Lords, I cannot defend a man when I have not considered every aspect of the case. I must have time to examine witnesses, read statements and to prepare my case.” He just loves the whole court atmosphere, doesn’t he?

Things to love about this episode number one – the hats of the three judges. You don’t often see hats as impressive as this.

Things to love about this episode number two. Raf De La Torre is the senior judge and the only one to have a speaking role. The other two (played by Alan James and Peter Stenson, who doubled up with other roles as well, playing Voords, Ice Soldiers, etc) are noteworthy for several reasons. The first is their stick-on beards and the second is their excessive head movements when Raf De La Torre confers with them. Neither are allowed to speak, as they’re just lowly extras, so they indulge in manic head bobbing instead. It’s a lovely moment of unintentional comedy.

The Doctor’s pretty smug. He’s convinced he knows who committed the murder (it’s elementary, he says) but he has no evidence. Using Barbara and Susan he demonstrates exactly how the crime was committed – but the problem remains, how to prove it?

Things to love about this episode number three – a classic Billyfluff. “I can’t improve at this very moment. I can’t prove this very moment.”

There’s some familiar faces to spot. Fiona Walker, who returned to the series twenty four years later as Lady Peinforte in Silver Nemesis, is Kala. Donald Pickering, whose Doctor Who career culminated (if that’s quite the right word) with Time and the Rani is Eyesen. I love watching Pickering as he’s always a compelling screen presence. It’s not much of a role, but with a less skilled actor it wouldn’t have been half as interesting.

And what’s the Doctor’s plan to prove Ian’s innocence? He gets Sabetha to perjure herself by pretending that Aydan (Martin Cort) gave the key to her. Not quite the sort of thing that you’d expect to see at the Old Bailey. Aydan’s startled admission of guilt (and his murder immediately afterwards) moves the case on a little. But it doesn’t prove that Ian is innocent, so his execution will take place at the designated time. Ian looks at the Doctor, who can only shake his head sadly, which isn’t very encouraging.

And then Susan is kidnapped. Eek!

It was David Whitaker’s idea that the locations of the story should be quite varied – one week a jungle, the next desolate snowy wastes. This is something that doesn’t occur very often in Doctor Who – normally when the TARDIS lands we’re never expected to wonder what the rest of the planet might be like. Often (picking a few random examples – say, The Daleks and The Krotons) it’s strongly implied that everywhere else is of little interest and where the Doctor is now is all that matters. But The Keys of Marinus, which shows us several cities ruled by different people as well as more barren locales, is quite different and should be applauded for that.

Last time, we left Ian and Barbara freezing to death in the fake snow. Luckily(?) they’ve been rescued by Vasor (Francis de Wolff) a man who lives in a hut all by himself in the middle of the snowy wastes. He shows Barbara how to restore life to her frost-bitten hands (doing so in a way that carries a certain overtone – it’s clear that he enjoys holding her hands in his). Indeed, there’s no two ways about it – Vasor is clearly keen for Barbara to spend some quality time with him (just as soon as he’s got Ian out of the way) and it’s equally clear what he wants to spend this time doing. It’s not spelt out, but then it doesn’t really need to be.

Ian sets out to find the others and hands over his travel dial in exchange for some of Vasor’s furs. Although Vasor, as scripted, tells Ian to pick up a coat and gloves, he only puts on a ratty piece of fur – which can hardly be expected to offer a great deal of protection (a poor bargain for his travel dial). Once Vasor and Barabara are alone he insists on feeding her some more food. “We must fatten you up, eh?” Brrrrr, I don’t fancy Barbara’s chances ….

Ian discovers Altos unconscious in the snow, but once Ian’s rubbed some life into his legs he seems able to carry on (yes, you can read something homoerotic into this if you wish). Luckily for Barbara, the two of them get back to the hut before Vasor’s been able to have his wicked way and the four of them then go back out to look for Susan and Sabetha.

They’re taking shelter in the ice caves, which is a decent-looking set. The Ice Soldiers, frozen warriors who are guarding the micro-key, aren’t quite so impressive though. This is another of those inexplicable Arbitan moments. The micro-key is contained within a solid block of ice, but if they melt the ice then the homicidal Ice Soldiers will wake up. Arbitan certainly didn’t like to make things easy, did he?

The excitement level as our heroes are pursued is fairly low – although Vasor gets his long overdue comeuppance from the Ice Soldiers (a sword in the back). Not the best episode of the story then, but Francis de Wolff (at times overacting like a good-un) is entertaining enough.

Next time, Ian faces a sentence of death.

It’s not really correct to think of the Voord as the villains of the story as they only appear briefly in episode one and then not again until episode six. Had they decided to shadow the Doctor and his friends as they quested for the keys that would added a little extra excitement, although with their wetsuits and big flippers they probably would have stood out somewhat.

Carole Ann Ford wasn’t particularly enamoured of the way Susan was portrayed in this story and it’s not hard to see why – she seems to be written down in age somewhat (acting more like a very young child at times). So given how hysterical she is in the jungle setting, it’s a blessed relief she’s packed off to the next location pretty quickly.

Things to love about this episode number one – the jungle vines that attack Susan in a less than convincing way.

Things to love about this episode number two – the statue with human arms which gives Jacqueline Hill a quick grope (although in the interests of decency it’s lucky that it could only reach her lower legs).

When they find the micro key in the first few minutes, it appears that this episode will be ending twenty minutes early. Sabetha, Altos and Susan head off for the next location whilst Ian stays behind to look for Barbara. But the key is a fake, meaning that Barbara and Ian still have to find the real one. Slimming down the cast at this point isn’t a bad move since it would have been a stretch to find something for five characters to do (even worse if the Doctor had been there as well).

And since Ian and Barbara are left alone it allows them a decent share of the action. Indeed, had it been decided at the end of The Velvet Web that Sabetha, Altos and Susan should search for the third key, whilst the Doctor went off to look for the fourth, then they could have dispensed totally with the services of Carole Ann Ford, Robin Phillips and Katherine Schofield for this episode and the production would have saved itself some money.

What Ian and Barbara find is a building full of traps. At times, all the suspension of belief you can muster is required – especially when Barbara is menaced by slowly descending spikes (of the patently rubber variety). It’s the sort of thing you might expect to see in a 1940’s Flash Gordon serial, although done somewhat better. And whilst Barbara faces death of an especially unconvincing kind, Ian is struggling to free himself from a prison of solid iron bars.

Except that they’re not solid – it looks like one sneeze would cause them to collapse. Just as it takes all of Jacqueline Hill’s professionalism to make us believe that the spikes are dangerous, so William Russell has to call on his acting experience to make the bars seem solid. Bless them both, they don’t quite succeed but it’s fun to watch them try.

All these traps have been set by Darrius (Edmund Warwick). Rather oddly he tells Ian and Barbara that only couriers sent by Arbitan would have been able to negotiate the hazards that he’s set. But Arbitan didn’t pass this information on – simple absent-mindedness maybe?

The silliest episode so far, it’s somewhat disposable fare – but at least one of the good things about this story is that we’re never too far away from a new location. And as the cliffhanger looms, Ian and Barbara find themselves menaced by some fake snow …..

The first stop on their quest to recover the keys of Marinus takes them to Morphoton. It’s a place where every whim and request is able to be indulged – although if this seems too good to be true it’ll probably comes as no surprise to learn that it is.

This episode is notable for having more edit points than was usual at the time – this was in order to demonstrate the difference between Barbara’s viewpoint (she can see their room for what it is – dirty and bare) and the others (they’re conditioned to view it as opulent). In later years this would be a scene that wouldn’t be at all remarkable, but when watching sequentially it’s another of those small moments which does stand out.

It’s maybe right that Barbara – the voice of reason – should be the one not to fall under the spell. But this wasn’t through any demonstration of free will, it was only because the conditioning disc placed on her forehead slipped off during the night. Note to the brains of Morphoton – it might be better to find a more effective way of conditioning your subjects (or at least use better glue).

The episodic nature of the serial means there’s not really time to develop the horror of Barbara being totally isolated.  She’s the only one of the four to retain her own memories (the Doctor, Ian and Susan have all been thoroughly brainwashed). This is a pity as the concept would have produced good material for several episodes. But there’s still the odd creepy moment, such as when Barbara rushes to the reassuring presence of Ian – but immediately after she’s embraced him it’s clear from his immobile stance that he’s no longer the man she knew.

We meet Altos (Robin Phillips) and Sabetha (Katherine Schofield). Both will join the others on the quest (Sabetha is Arbitan’s daughter and Altos is one of Arbitan’s couriers). Their presence is a good thing, especially as Billy’s shortly off for a two-week holiday. They’re fairly stock Terry Nation characters, so how well they come across depends on the actors (who do the best they can).

The brains of Morphotron are a little disturbing (especially the way they’re voiced by Heron Carvic) although the black and white picture does rob them of some of their impact. Barbara saves the day by smashing their brain cases and killing them. Or, at least, that was how it was scripted – alas, Jacqueline Hill only managed to smash one of the four cases and there was clearly no time for a retake. Oh well.

The Doctor’s decided to nip ahead and look for the last key (so we won’t be seeing Hartnell for a few weeks) whilst the others head to their next destination.

And it’s a Terry Nation favourite – a dangerous jungle!

By going from Marco Polo to The Keys of Marinus we’ve taken a trip from the sublime to the ridiculous. That’s not to say that Marinus is bad – it’s good, pulpy fun – but when watching the series sequentially it’s a little jarring to have this sudden shift in tone. But that’s one of Doctor Who‘s great strengths – the fact that every new adventure might play out in a totally different way from the previous one.

You have to admire the ambition of Verity Lambert’s time as producer. It seems that no story was too ambitious to mount (think of the expertly created props in Planet of Giants or the sheer weirdness of The Web Planet) and Marinus is another example of this. With such a tiny budget the notion of creating a new environment in episodes two, three, four and five obviously placed a huge strain on the meagre resources of Ray Cusick. He manages to pull it off quite successfully, although there are times when you do need to be a little forgiving.

The miniatures that open the story are excellent though. The shot of the island – with a model TARDIS (light flashing) then appearing – is a lovely one. The sight of the Voord’s submersibles traversing the sea of acid is less effective though – mainly because it’s painfully obvious they’re being pulled along by wires (and one of them is reluctant to move, so requires a few hard tugs to enable it to reach the beach!)

The sight of the Doctor, Susan, Ian and Barbara surveying this strange new planet shows how far we’ve come since The Daleks. Back then, Ian and Barbara were wracked with fear and doubt (hating the fact that they’d been uprooted from their safe, 20th century existence) but now they regard this bizarre island with nothing more than mild curiosity.

Hartnell’s a bit stumbly over his lines in the early part of the episode (which gives us one of his classic Billyfluffs – “yes, and if you’d had your shoes on, my boy, you could have lent her hers”). This part of the story – as the four examine the beach – is a little problematic. Given that the studio was so small, the beach set couldn’t be particularly large either – which becomes painfully obvious when everybody has to walk around rather slowly.

The moments when they notice the Voord’s submersibles and Arbitan’s building both seem false – there’s no way to imply that they’ve travelled any distance from the TARDIS, so these things must have been under their noses all the time.

I know that examining logical loopholes in a Terry Nation script is a little futile, but the sight of the Voord suit – which contained a man who’s been destroyed by acid – has always irked me. If the suit had a rip then that would have let the acid in, but he was inside a submersible – so that too, must have had a hole (which is rather unlucky really). And if that was the case, wouldn’t the submersible have been full of acid?

Why does Arbitan’s building allow people to enter? You’d have thought it would have made much more sense to keep them outside (and since the Voord don’t seem to have any particular weapons, an impenetrable wall seems as good a barrier as any). Instead, its obvious that although there’s interior defences, sheer force of numbers will allow the Voord to succeed once they do get inside.

It was a bit of a coup to get George Coulouris to appear as Arbitan, although he was no stranger to low-budget British science fiction, having appeared in ITV’s Pathfinder trilogy. He’s the Keeper of the Conscience of Marinus and he explains to the Doctor and his friends exactly what the machine does. “At first, this machine was simply a judge and jury that was never wrong or unfair. And then we added to it, improved on it, made it more and more sophisticated so that finally it became possible to radiate its power and influence the minds of men throughout the planet. They no longer had to decide what was wrong or right. The machine decided for them”.

And Arbitan wants the Doctor’s help to restore the machine’s power! The notion of anybody being denied free will would later become something the Doctor would fight against time and time again (for example, The Masque of Mandragora) so it’s astonishing that he sees nothing wrong with this machine.

Thanks to a handy bit of blackmail with the TARDIS (the Doctor’s still the type of person not prepared to launch into a dangerous adventure just for the fun of it – that will come a little later) Arbitan persuades the four time-travellers to set off for a jaunt around Marinus to recover the four keys that will restore the machine to its former glory.