Really, there’s no more time for these absurd theories.’

Doctor Who can go anywhere in time and space, and visit any alien planet or historical figure it pleases – that’s rather the point of the show, after all. But in only the third serial, the production team decided to set a story entirely inside the TARDIS, with no other cast than the regulars.

Simon Guerrier has ten theories relating to this most unexpected of early stories, and one about the readers of this Black Archive…