The sleep industry is worth £350 billion. It’s hardly surprising: chronic insomnia affects more than a tenth of adults, delivering a panoply of gritty side-effects including shaving up to five years off your life (according to recent research from Harvard Medical School). Finding a solution can be time-consuming, frustrating and costly, usually ending in dashed hopes rather than eight golden hours. For many, the search for a panacea involves traipsing from doctors to soothsayers to Instagram.