When your role in life is to gander over each and every horizon, an unknown space becomes a priority. Arven Fisk, a tall and scruffy man with bright green eyes, had glanced from the window of his temporary residence on the High Street that morning to realise that he’d never walked the west bank of the Black Lake from Hogsmeade. And so he set out to do so immediately, wrapping his pet ferret Virgil about his shoulders and throwing on his long coat to ward off the unseasonal chill.

The day was a pale silver colour, but the Black Lake was bluer than forget-me-nots. When Arven looked at it he thought of his years at Hogwarts, splashing in the water with his friends during the hot summers, skimming the surface on a broomstick, observing the lakelife and “conversing” with merfolk. So as he went west at the Docks and took the narrow path between the forest and the lake, he knew to expect quite a nostalgic stroll.

Until he saw something bobbing out in the lake and wondered what it was.