Alderley Edge is a sandstone ridge rising 180 metres above the Cheshire plain, a dozen miles south of Manchester. The Edge itself, now owned by the National Trust, has become a honeypot for Mancunians, and the village below, formed by the railway as a commuter dormitory for Manchester cotton-kings, is now nicknamed the champagne capital of England. Beneath lie copper and lead mines and, according to legend, a sleeping king and his knights ready to save England in the last battle of the world. In 1953 the schoolboy Alan Garner rediscovered an old wooden shovel found in the mines; nearly forty...