Having created what would become The Doctor’s most famous and best-loved enemies in The Daleks (1963-1964), Terry Nation returned with a very different story, The Keys of Marinus, a sprawling six-episode epic. If nothing else, it again demonstrated just how flexible Doctor Who‘s format was and the lengths to which the writers and producers would go to test that flexibility to the limit. It’s an ambitious story but not one that works particularly well.

The TARDIS materialises on a small island o the planet of Marinus where The Doctor (William Hartnell), Susan (Carole Ann Ford), Ian (William Russell) and Barbara (Jacqueline Hill) meet Arbitan (George Coulouris), Keeper of the Conscience of Marinus, a huge super-computer designed to help maintain law and order on the entire planet. They learn that the Voord, a race of amphibian humanoids are trying to take control of the Conscience and that to prevent them, the Conscience needs five keys that have been scattered across Marinus. With the TARDIS trapped in a forcefield, the crew are forced to agree to help find them, visiting first the city of Morphoton, which turns out not to be at all that it initially seems and where they recruit slaves Sabetha (Katharine Schofield) and Altos (Robin Phillips) on their journey; The Doctor heads for the city of Mellennius while the others are trapped in a screaming jungle; Barbara becomes lost in an ancient temple where she and Ian meet aged scientist Darrius (Edmund Warwick), who reveals the location of the next key; Ian and Barbara are then teleported to an icy wasteland where the trapper Vasor (Francis de Wolff) steals their keys; The Doctor’s companions are put on trial and only the timely return of The Doctor can save them. But have they done enough to prevent the Voord from seizing control of the Conscience?

As even this most cursory of plot outlines suggests, The Keys of Marinus is episodic but full of action. Sadly a lot of that action is very repetitive, a fault that would dog many of Nation’s scripts, a tendency to run round and round in circles instead of charging headlong into the plot. But to give him his dues, Nation does hold the distinction, not always acknowledged, of getting us to exactly the halfway mark in series one being the only writer to have actually created any aliens for the show. Back on Skaro, the Thals had been a bit wet but the Daleks of course became iconic, almost as synonymous with the programme as The Doctor himself. The Voords… well, they were less impressive. With costumes made for under £70 (about £1,134 today) they were always going to look a bit cheap and Sydney Newman must have throw up his hands in horror when he saw them, though he was no doubt comforted by the fact that his famous edict to not feature “bug eyes monsters” in Doctor Who was given considerable weight by the silly looking men if frogman suits. Fortunately, the Voord don’t feature that much, and they were never seen or heard from again on screen.

But the Voord aren’t the serial’s only problem. Apart from not getting a handle on how to pace a 6-parter, Nation – despite being the show’s first returning writer – still hadn’t worked out how to write for Susan. She’s much less mature here than she had been in the previous couple of stories (she does a lot more crying than usual), perhaps more in keeping with her still being a schoolgirl. Maybe that’s not Nation’s fault – perhaps the production team, as a whole hadn’t quite got a handle on her yet. More damaging, and something well beyond Nation’s control, William Hartnell’s absence from episodes three and four (he was on holiday at the time) is very noticeable and while it gives the other regulars another chance to shine, he’s very much missed.

Despite the quest storyline, there’s very little sense of urgency in the search, a lack of energy not helped by the story juddering to a halt for the trial scenes. the skipping from one location to another gives the story the feel of one of the serials of old, but it proved a challenge to the budget, designer Raymond Cusack having to conjure up more than the usual amount of sets for, presumably, not much more money. For the most part, he does a fine job but there’s some very obvious penny-pinching on show. And no matter how hard Cusack’s sets work, they simply can’t distract us from the fact that for all the TARDIS crew’s running around on an alien planet, not much of interest happens to them along the way. Story editor David Whitaker could have done with a heavy-duty pass over the scripts, trimming down to a more manageable four episodes which might have injected a little “oomph” into the proceedings.

The more one engages with Doctor Who fandom, the more one comes to realise that every story has its fan. Yes, even Warriors of the Deep (1984) will have its defenders, though the search for those willing to publicly express their love for Time-Flight (1982) might take a little longer. The Keys of Marinus has its admirers, perhaps charmed by oddness of the Voord, and certainly impressed by the sheer scale and ambition of the scripts. But it all too often feels like harder work than it really should be, sluggish, listless and ultimately leaving us with the sense that we’ve travelled a long way for very little reward. Thankfully The Aztecs (1964) was up next and was an altogether more interesting and entertaining tale.