"The economists' old friend, the supply and demand curve, is a fairly reliable indicator of what foods are used to signal high status: venison and game, the sale of which were highly controlled, from the Norman invasion onwards; spices in Medieval and Tudor England; French food in the 19th century," she says. "For centuries anything imported was high status – and we still grant 'middle class' to imported foods such as avocado or quinoa – even though they might be peasant foods in their countries of origin."