I quite like this one. The incredibly versatile Bernard Kay is clearly the most interesting character by a mile, although Ashe (a brilliant John Ringham who couldn't be further from the slimy Tlotoxl) and his daughter (a young Helen Worth AKA Gail from Coronation Street!) add a certain amount of colour. But the robot is dismal, and I think this one of Jo's very worst stories. She's absolutely hopeless. A trio of trios (the three species within the caves on Uxarieus; the three members of the I.M.C.; and the three groups themselves) help to focus the story, which I think is one of Malcolm Hulke's most political, and (not coincidentally) one of his best.

There's not many Pertwee stories I will re-visit again and again, and this is not one of those few. But it is nearer the top of the pile for me, and a highlight in what for me is a very shaky series.

They way the TARDIS just pops in to existence without the classic Vworp Vworp noise or fading. An all round decent first of planet story of three and a good trip in to space and whilst they may repeat significant elements of this narrative over the rest of Pertwee’s run. It never gets old and gets on a grange better each time.

The various Uxariean subspecies are some of the most laughably bad creature designs the show has had in quite some time (potentially even rivalling The Web Planet's aliens in terms of lameness). The Guardian in particular is such an utter joke that I'm amazed no one at any phase of the production spoke up or tried to do anything to make it seem even the slightest bit more imposing. For what is seemingly an all-powerful and omnipotent creature, its high pitched voice and shrivelled up baby body make it look and sound completely ridiculous, and renders any scene featuring it completely devoid of atmosphere.