"I don't know anyone who grew up in the 1970s who wasn't scarred by the public information safety films on British TV. Those tiny, doom-filled dramas slipped in between the cartoons were often only fifteen or thirty seconds long but, by God, they caught our attention. Don't play with matches, or old fridges. Or kites or frisbees, should you happen to be near a pylon or electricity substation. Be careful crossing the road and running along the beach. And also near ponds and lakes, or when swimming in the sea. And never, ever talk to strangers.

And then, of course, there was Protect and Survive. A full set of instructions for what to do in the event of nuclear war. Coming from a time of such existential dread, is it any wonder that those films are now considered a cornerstone of the UK's collective Horror imagination?

I'd wanted to use them in a story for a long time, but the idea lay dormant until I realized two things. Firstly, that there was an element of warding ritual and incantation to them ("Look left, look right...", "Charley says...") reminiscent of folk horror, only in the urban environment rather than the usual remote rural setting. And, secondly, that those films were what Britain was scared of fifty years ago. What I ought to be writing about was what really terrifies me about this country now."