Right at the very end, The Mind Robber‘s grasp falls short of its reach. But up until then, the last episode maintains the pace and creativity of its predecessors which, combined with Troughton’s most intense physical comedy, ensures this will endure as one of the  most memorable of all Doctor Who serials.

Troughton’s performance, rarely less than excellent, has been more critical than ever to a story that otherwise lacks any sense of internal logic, or, really, any other proper characters beyond the Doctor, Jamie and Zoe – and even Jamie and Zoe are robbed of their own identities for the bulk of this episode. He’s at his most Buster Keatonish here – climbing up a bookcase, leaping across battlements, and sitting disconsolately amid fictional characters as he contemplates his own fate.

The notion behind this episode, of the characters taking control of the writing to create the conclusion, is astonishing, and if neither the writer nor director quite work out how to pull it off (their best effort is to have the Doctor sitting at a typewriter bashing out script pages), the idea is strong enough to be compelling. It’s almost a shame that mundane villainous concerns are allowed anywhere near this – as it is, there’s some vague references to conquering Earth and leaving it depopulated, but the details are left vague.

The story’s theme is left similarly vague: ‘Don’t worry about fiction. Hang on to real life,’ the Doctor urges Jamie and Zoe. This, combined with all the earlier scenes of him imploring them to deny the reality of fictional creatures, suggests some concept of putting away childish things and facing the world as it is, rather than running away into fairytale whimsy. If so, it’s either as reactionary as The Dominators‘ rejection of the anti-war hippy generation, or a call to action against controlling colonisers in the spirit of the 1968 protest movements. Whether Ling intended either reading, or whether I’m reading too much into a handful of lines is debateable. Perhaps the only message in the end is not to take any fiction too seriously.

And although, right at the very end, the climax consists of pressing some buttons randomly while the White Robots accidentally shoot the Master Brain, everything is happening with such chaotic energy at this point that it’s barely noticeable. The Mind Robber is the most 1960s of all Doctor Who stories, mixing a sort of nostalgia for childhood, with an awareness of how cruel and frightening it can be. The ambivalent climax – the TARDIS simply reforms as the regulars flee through a black void –  ends the story in disturbing, dreamlike darkness.

Next episode: The Invasion