The common consensus about this story is that it has an intriguing first episode but this early promise is then squandered as the remaining three installments consist of little more than a lot of tedious running about. Some, like Rob Shearman, have mounted vaillant defences on its behalf – but I think its reputation as an also-run is fairly safe.

Although saying that, it’s not a total disaster and it’s true that the opening episode does show plenty of promise. What’s unusual about this one is that it does attempt to show some of the consequences and paradoxes of time travel – an area which the series rarely tackled during its original run (Day of the Daleks, Pyramids of Mars and Mawdryn Undead are three fairly rare examples off the top of my head).

We open with a mystery – in the first few seconds the four time-travellers are still dressed in their garb from The Crusade, but seconds later they’ve changed into more familiar clothes. But since they don’t remember doing it, how has it happened?

The Doctor at first doesn’t quite get Ian’s drift when he tells him that they’re wearing their clothes (“well, I should hope so, dear boy. I should hope so”) but then airily dismisses their concerns. “You know, it’s so simple. It’s time and relativity, my dear boy. Time and relativity.” When asked to explain further, the Doctor claims he doesn’t have the time, but it’s obvious that he doesn’t have a clue!

Other strange instances – time runs backward after Vicki breaks a glass – are further puzzles, although these are harder to explain. If the Doctor’s later conjecture that they’ve jumped a time track is correct then that could explain the clothes issue – somehow the TARDIS has pushed them into their own future, so it would be reasonable they weren’t wearing their crusading costumes – but the glass/water mystery is more inexplicable.

Of course it could be that our old friend the TARDIS was attempting to raise the alarm that something was wrong (as it did during The Edge of Destruction). If that’s the case then it was with just as much success (i.e. not very much).

There’s an eerie feel to their initial investigation of the Space Museum. Although the four time-travellers seem corporeal and solid, it’s later revealed that they’re little more than insubstantial phantoms – unable to leave footprints in the dust, touch objects or speak to the inhabitants. When they find themselves displayed as immobile exhibits in the museum it’s a striking moment. In this version of the future the Doctor and his friends were captured and turned into exhibits, but that’s only a possibility – it doesn’t have to come to pass.

So they have the chance to change the future and ensure that this grisly occurrence doesn’t come to pass, but how to proceed? Should they go straight back to the TARDIS and leave? Or would that lead directly to the cases?

This part of the story is undoubtedly the highlight as it helps to raise the stakes of the adventure a little more (if they fail then they already know their fate). It’s also fair to say that had this started as just a normal adventure, without this timey-wimey subplot, then The Space Museum would be even less of interest than it currently is.

And we get to see a Dalek! Albeit as an immobile museum exhibit like everything else. It’s a nice foreshadowing of their imminent reappearance (you have to love Ian’s comment that it’s highly unlikely they’ll ever meet them again – I doubt many in the audience were convinced). What’s slightly odd is Vicki’s comment that she’s never seen an image of a Dalek, although she’s read about them in her history books. It’s hard to imagine that there wouldn’t be some visual evidence or photographs of them available during Vicki’s time.

The stock music is at times rather overpoweringly dramatic, although some of the tracks are successful in creating the required odd atmosphere. With the four regulars the only actors with speaking parts (at least speech that we can hear) it’s an excellent vehicle for all of them. For example, Vicki gets some dialogue which shows that whilst she (like Susan) may be sometimes written as a mid twentieth century girl, she’s most evidently not. “Time, like space, although a dimension in itself also has dimensions of its own.”

A more than decent opener, but what will happen when we meet the Moroks and Xerons?