If innovation has an iconography, it involves a genius, a breakthrough and a dash of serendipity. Alexander Fleming notices mould growing on a plate of bacteria and discovers penicillin. John Snow produces a map of the victims of a cholera outbreak in 19th-century London and traces the outbreak to a single water pump. A German chemist called August Kekulé falls asleep, dreams about snakes eating their tails and realises upon waking that the benzene molecule has the shape of a circle.