For centuries, London was the world's largest city, and a frontline in mankind's battle against disease. Dr Richard Barnett explores how city life has been shaped by sickness and health. London's geographical location has been both its blessing and its curse. The river has at different times offered the health hazards of both malarial swamp and open sewer, but it has also been a global trading route bringing exotic commodities and foreign cures. Read by Tony Gardner.