London sewer system

The clearest natural experiment on the list came from the one district the system had not yet reached. Joseph Bazalgette's sewers were begun in 1859, after the Great Stink of 1858 finally forced Parliament to act over the state of the Thames, and completed in 1875. In June 1866 cholera broke out in east London, where homes were not yet connected. William Farr found 93% of deaths fell within the East London Waterworks Company's area, where about 4,000 people died, while the rest of the city was spared. Bazalgette installed temporary pumps at Abbey Mills and within weeks diverted local sewage into the new Northern Outfall sewer. It was London's last cholera epidemic.