After an exorbitant recap this turns into a string of capture/escapes which could be tedious except each one brings the Doctor and Jo in touch with different groups, and helps to advance the plot and establish the opposing sides in a way that’s reminiscent of Hulke’s work on The War Games. While the Doctor is captured by the Draconians and threatened with the Mind Probe, Jo remains an Earth captive, subject to the same threat, and the script reinforces the parallel by cutting between the two scenes. This sets up the idea of the Draconians and humans as equal and opposite forces, before the end of episode arrival of the Ogrons confirms the involvement of a third party.

It’s quite an elegant structure, and the connective tissue is pretty strong as well. Pertwee gets a “moment of charm” as he tries to reassure Jo with an anecdote about the Third Intergalactic Peace Conference, before doing some Venusian karate on the Draconians. His double act with Katy Manning is brilliant: the Doctor’s initial indulgence and then mounting exasperation as she proposes various prison break schemes is lovely, and Jo’s increasing ability to take the lead (while the Doctor sits back as if assessing her) is another mark of her development as a character.

Design and location work are strong as well. The South Bank provides exactly the kind of brutal concrete architecture that will become BBC sci-fi shorthand for dystopian urban futures (perfected in Blake’s 7, which this, with its cocktail-dressed Madam President and her sporty male subordinate, clearly predicts). The Draconians are great creations: John Friedlander’s masks are excellent, and some thought has also gone into giving them costumes rather than just scaly body suits that suggest nudism is rife in outer space. This means when we’re faced with a couple of chatting Draconians we aren’t dealing with the tedious monotone burbling of the Cybermen or the comical bobbleheaded mannerisms of the Silurians, but with two alien people having a chat (I love the script’s subversion of their generic Samurai aesthetic by having them refer to the humans as an ‘inscrutable species’). This is really good fun so far.

Next episode: Frontier in Space – Episode Three