Hartnell gets his first chance to impress for a few weeks as he confronts the disembodied voice of his captor. Accused of being the vanguard of an invasion fleet, he defiantly grips his lapels and goes on the offensive, high-handedly lecturing the voice. What’s really impressive is his ability to dominate the TV screen, narrowing his eyes or darting them back and forth, taking it all in. He may fluff his way through a couple of scenes, but his physicality and presence are amazing.

Having reached an understanding with the ‘Queen of the Ants’, the Doctor gets to bring Ian in on his plan to outfox her – a plan that involves using the Astral Map (yay!) to distract the enemy while Ian escapes the great web and goes to find Barbara.

Sadly this rescue attempt involves Ian wrestling a giant ant before a very prosaic door with a half-hearted web pattern painted on it swings shut on him. After several minutes of bleeping insects inexplicably dashing about, it’s a relief to rejoin the Doctor as he smugly confronts the disembodied intelligence.

At the Crater of Needles, Ian meets a Menoptra called Vrestin that tells him the story of the Animus and its weaponisation of the Zarbi. The Menoptra fled to a ‘strange moon’, a ‘dim half world’, but they long to return to Vortis before the Carsenome consumes the entire planet.

Perhaps because this is one of the most-watched Doctor Who serials ever, it seems to have lodged in a lot of imaginations. The second Doctor has his own battle against a disembodied intelligence that imprisons the TARDIS in a web, and the interior of the Carsenome with its weird waving fronds is very like the later Axon spaceship.

Next episode: Crater of Needles