Towards the end of the episode, Jamie, already irate from being shot by the Ice Warriors and dragged through miles of snow, bellows at Clent, ‘You’ve got to do something!’ But the episode – and the story – involves doing nothing; uncertainty leading to prevarication, and ultimately a fatal avoidance of trusting to human instinct and making a choice. It’s definitely thematic – earlier in the episode, when they’re threatened by a bear, Penley tells Jamie they need to stay absolutely still: under pressure he, like Clent, is ‘a scientist, not a gladiator’, gripped by intellectual weakness and only spurred into action by Jamie’s instructions to shoot the animal. The problem with all of this is watching people vacillating just isn’t very interesting.

This week, even the mighty ‘computer is playing for time’ – like the Tellurians and the Martians, it’s frozen with indecision. Because neither it, nor Clent, knows whether using the Ioniser will create a nuclear holocaust. As the Doctor outlined this problem way back at the start of Two, the script’s lack of progression is annoying. I can appreciate a game of who blinks first, but this is really pushing it.

It’s not just that the story is moving at such a glacial pace, it’s that the characters don’t even seem to be consistent. Clent, who seems to be thawing a bit at the start of the episode suddenly seems to have some sort of fit when Jamie and Penley arrive at Britannicus Base and orders them shot. And Garrett, who a fortnight ago trudged through the tundra to beg Penley to return as ‘the only one who can help us’ now tells Clent that ‘he can’t be allowed to interfere’ and utterly rejects him in favour of the computer.

This is all very bad indeed. Patrick Troughton and Deborah Watling do their best with some comedy business with a stink bomb, and Derek Martinus tries manfully to make the cutest of bears look threatening – but it all seems very much like the attempts to make Homer look like a monster in Homer: Badman

Next episode: The Ice Warriors – Six