I often find it odd that Earl Grey is an almost ubiquitous beverage, whose tell-tale floral perfume scents teacups the world over, and yet its key ingredient, the bergamot, is a rare specimen whose glowing presence amidst the jumbled crates of a farmers market stall is guaranteed to send serious food-lovers into paroxysms of excitement (and, subsequently, to lead to heightened activity on Instagram as we first show off our esoteric citrus haul and, not long after, start crowdsourcing suggestions on what on earth to do with this highly underrated and underused knobbly lemon thing). Earl Grey is available in myriad forms, from high-class zesty loose leaves for infusing in china teapots to the tannic dust likely to fill your cup in a greasy spoon café or on an aeroplane meal tray. That the actual source of these plentiful, cosmopolitan cuppas remains elusive is one of the strange realities of our modern food supply system.