1964's

My aesthetic is Moffat allowing himself to be such a fanboy when writing his final scripts that he makes references that the official Doctor Who site doesn’t get.

(Pictured is an excerpt from “The Doctor Falls: The Fact File” on the Doctor Who site. It reads “A more unexpected reference is the Doctor’s mention of Marinus. The planet has only been visited once onscreen, in the fifth ever Doctor Who adventure, 1964’s The Keys of Marinus. Curiously, that story made no mention of the Cybermen. Indeed, the ‘tin men’ from Mondas wouldn’t make their debut until over two years later!” Obviously no one told them about ‘The World Shapers’, a 1987 comic from Doctor Who Magazine that claims that Marinus is an early Mondas, and that the Voord are early prototypes of Cybermen!)