High on a deserted Welsh hillside, on the edge of a deserted slate quarry, Freema Agyeman, playing Martha Jones, films some of the last scenes in the new series. Something pivotal, which I’m not allowed to tell you, is happening to the Earth, in a time I’m not allowed to reveal, and Jones is watching the whole thing unfold from behind a rock. The rock, I can reveal, is grey and quite large. It is about the only thing within view that isn’t top secret.

John Simm’s entrance is intense and low-key. As the pivotally evil Mr Saxon, Simm is in a black suit, wearing an ominous-looking ring and eschewing the buffet in favour of a quiet lunch in his trailer. “I can’t tell you anything,” he says, sighing. “I don’t think I’m even officially here, am I?” He shrugs.