Both cities progressed rapidly from manufacturing to industrial to financial capitals, and in the process, voraciously abetted by the appetites of their citizenry, both killed their oysters (Paris, the third great oyster metropolis, protected its beds far more successfully, and to this day shuckers presiding over crates of oysters packed in ice remain a common sight on the city's corners in winter).

ECONOMIST: A dozen ocean-cleaners and a pint of Guinness, please