This is a really good episode for all the regulars. William Russell is finally getting to be the hero again – rescuing the Doctor from becoming an exhibit, and forcing Lobos to reverse the freezing process. Having incited armed revolution, Vicki heads back into the Space Museum to search for her friends. And Barbara is the one to drag Dako to safety from the Morok gas attack, before she gets to reflect on their existential dilemma, and finally cleverly defuses a brewing temper tantrum by the Doctor. As this is practically the last time we’re going to see the whole team together, it’s a lovely last hurrah.

There’s a lot that’s not so great about this episode and the serial in general. The plotting rarely lives up to the concepts – with way too much time spent wandering about corridors, or on flabby dialogue scenes where the potential in the material is deflated as the performances aren’t sharp enough, and the comedy isn’t funny enough.

However, The Space Museum gets more right than it gets wrong. There are several elements that foreshadow later series standards – in The Final Phase this includes a scene of Morok soldiers trying to break into the TARDIS that plays out again and again through future episodes and various hostile aliens.

Plus, the resolution to the story is absolutely excellent. Having learned that you can’t change history, not one line, Barbara fatalistically ponders whether all their choices have led them inevitably to the point of becoming exhibits. But the Doctor points out that while they’ve been on Xeros ‘we’ve met people, spoken to them and who knows, we might have even influenced them.’ They (and particularly Vicki) have inspired the downtrodden Xerons to seize control of their own destinies – and in so doing, change the destiny of the TARDIS crew.

It’s the kind of punchline that recurs during the Eccleston episodes when it’s not so much what the Doctor and Rose do but the impact that they have on the people they meet – Dickens, Captain Jack, Pete – that is their salvation.

It’s entirely apt that at the moment this TARDIS crew become the stuff of legend, the Daleks recognise them as ‘our greatest enemies’. It’s a brilliantly unexpected cliffhanger that cleverly pays off the appearance of the Dalek exhibit in the earlier episodes – just as the TARDIS crew have avoided becoming frozen, dead exhibits, so the Daleks have come back to life, as though somehow they’re linked, locked in a life and death struggle across time and space.

Next episode: The Executioners