This article was first published in the July/August 2025 issue of IQ, the exclusive magazine for Mensa members. Find out more about becoming a Mensa member here.
Words: Katie Cutforth
How a summer heatwave and an unbearable stench was the catalyst for London’s sewer system.
Most of us welcome the warmer weather of summer but for the residents of London in the summer of 1858, it triggered one of the most disgusting crises in the city’s history. Dubbed “the Great Stink”, this event was more than just a bad smell – it forced London to rethink how it handled a basic business that most of us take for granted: managing the city’s sewage.
London’s population rocketed during the 19th century, rising from one million to almost three million in the first half alone – and more people meant more waste to dispose of. That, combined with the recent introduction of flushing toilets, meant more sewage than ever was filling the outdated sewers – some 40 million tonnes a year by the 1850s – and much of it was overflowing, or poured directly, into the Thames.
The toxic Thames
“Through the heart of the town a deadly sewer ebbed and flowed, in the place of a fine fresh river”, Charles Dickens wrote in the 1850s. Untreated waste, dead animals and industrial effluent all ended up in the river that had once been the pride of London.
The propensity of the Thames to make citizens retch had been a depressing reality for the city’s inhabitants for years but, in 1858, an unusually hot summer made conditions unbearable from June through to August. Soaring temperatures and dry weather caused the water level to drop significantly, exposing centuries of waste to the baking sun. The result was a stink the likes of which London’s poor residents had never experienced.
Foul smell, or ‘miasma’, was believed to carry disease, so catching a whiff of it was not only foul but terrifying, too. The smell had already been blamed for three outbreaks of cholera that preceded the Great Stink – though we now know that ‘drinking water’ taken from the Thames was responsible.
The Great Stink gave ample ammunition to satirical publications, such as Punch magazine, which depicted ‘Father Thames’ and his diseased children, who represented diphtheria, scrofula and cholera. During Parliament’s proceedings staff clutched handkerchiefs to their faces, and curtains were soaked in chloride of lime in an attempt to mask the smell.
From malodour to a marvel of engineering
As the anger of Londoners and concern for public health grew, politicians had no choice but to act. The then Chancellor Benjamin Disraeli (who would later serve twice as Prime Minister) tabled a bill, which was passed within 18 days. It made the Metropolitan Board of Works responsible for cleaning up the Thames and proposed the construction of a new sewer system that would prevent waste from entering the river within the boundaries of London.
Civil engineer Joseph Bazalgette led the design of a new interconnecting sewer system, which captured London’s waste and piped it out to pumping stations on the fringes of London. Waste still entered the river but far enough away from the urban centre to be deemed acceptable.
Completed over the following decades, the massive network of sewers not only cleared the pollution in the Thames but also helped to prevent deadly cholera outbreaks.
This marvel of Victorian engineering is still in use today. However, water companies in London and beyond are now coming under fire for the pollution caused by leaks and sewage spills, in part because of outdated infrastructure. The Great Stink has perhaps persisted, and continues to play out in the media.
Image credit: Shutterstock
