Where to begin. "It's an old British tradition - a little wooden puppet show, often performed for children at seaside resorts. Mr Punch is an outrageous figure who gets into appalling scrapes but gets his comeuppance at the end."

Nightingale flips to a clean page of his notebook and sketches a quick profile of a leering face with a half-moon shape, chin and nose hooked and jutting, an incongruously jaunty pointy hat topping the whole thing off.

"In the case I've mentioned, an unquiet spirit was using Mr Punch as a sort of avatar representing chaos, upheaval, the jostling anger of a crowd. The people possessed by this spirit had their faces twisted into his visage." He taps on the sketch he drew with his pen. "And when the spirit left them, so did whatever magic held the mangled remains of their faces together."