From the longer Wikipedia page [1] In the first 50 years of the 19th century the population of London more than doubled from 1 million to 2.3 million. At this time all London's dead were buried in small parish churchyards, which quickly became dangerously overcrowded, leading to decaying matter getting into the water supply and causing epidemics. There were stories of graves being dug that already contained bodies, and bodies being flushed directly into the newly-built sewer system.