The design of The Web Planet is largely pretty impressive. Early on in this episode there’s a shot of a vast arena seen through a fluttering web, with the surface of Vortis stretching to the horizon. It has a scale beyond even Skaro or Marinus.

This scale, and Strutton’s world-building is admirable – even if you don’t particularly like the story. Although Barbara and Hrostar have to share some exposition dialogue about the Animus and its control of the Zarbi, the man-in-a-moth-suit also reveals that the Zarbi have mutilated him so he will never fly again, which is weirdly upsetting.

Ian and Vrestin have been captured by another species on the planet – bringing the total to an impressive five different types of ‘monster’. The costumes of the Optera – sort of caterpillar grub creatures – are probably the least impressive. And they have the unfortunate habits of hopping about comically and talking like generic “natives” in 1930s movies (a pretty clear implication given their suspicion of the ‘outsiders’ who keep coming to their lands to explot), but again there’s a really likeable attempt to suggest they have their own distinctive culture and norms, which is reflected in the set’s cave paintings like an alien Tribe of Gum. ‘Freedom, peace, beauty and light’ are the ideals of the Menoptra – hiding away in the dark, like the Optera, is a recipe for ignorance and superstition.

All of this effort means that Vortis is easily the most ambitious environment visited by the TARDIS. While probably not as well realised as Skaro, it’s more alien – less like Flash Gordon pulp fiction and more like something highbrow by Robert Heinlein – with the audience encouraged to infer a lot from a few odd quirks of each of the alien types.

Meanwhile, the Doctor continues to put his wits against the Animus – bargaining for Vicki’s life with information about the imminent Menoptra invasion. Maureen O’Brien does a great ‘dozy face’ hypnotised expression whenever one of the Animus’ control collars is placed over her head.

Concluding with an impressive spearhead from space, and a full on battle between Menoptra and Zarbi, this has a lot of clunky moments that are almost laughable, but on the other hand is easily the most ambitious episode – both in script and production – that the series has attempted so far.

Next episode: Invasion