Down river

London is full of shit. More than four billion litres of effluent pass through its Victorian sewers every day. Much of that ends up at Crossness, on the southeastern bank of the Thames, where it is treated in vast steel tanks before being flushed into the estuary. For nearly a century, the capital’s waste flowed beneath one building that still sits along the riverbank: Crossness Pumping Station, a painted “cathedral of ironwork” completed by Charles Henry Driver and Joseph Bazalgette in 1865.

On a very hot summer morning, I joined three dozen urban explorers boarding a vintage double-decker bus at Abbey Wood station bound for an “open archive” day at Crossness, a special event hosted by the London Festival of Architecture. The bus would only take us part of the way; the rest was on a cherry red choo choo train called the Excrement Express. A sharp, sulphuric smell dissipated as the locomotive crawled towards the riverbank, past volunteer-run gardens planted with tomatoes and lavender. The air hummed with bees.

A man in a straw boater hat named Terry Wiggins greeted us on the path to three red-brick buildings. “Do you all like poo?” he asked. “I love a poo in the morning,” a man in the crowd offered. Wiggins said he’d spent 50 years as a chef for the House of Commons before joining the 100 volunteers who maintain Crossness as a garden, cafe and educational site. “Just don’t blame me for how things are going in Westminster,” he said.

The sewer system was born on a similarly hot summer’s day in Westminster. For centuries, London’s untreated waste flowed directly into the Thames, the city’s main source of drinking water. Successive cholera epidemics devastated the working class population in the first decades of the 19th century, until a heatwave struck in late July 1858. The odour from the river was so foul that parliament was suspended. When the “Great Stink” subsided in late August, parliament resumed and Bazalgette was commissioned to build the sewers.

One of the largest construction projects in British history, Bazalgette’s network consists of nearly 2,000km of brick-lined tunnels. Crossness was the crown jewel of this subterranean empire. In the centre of the engine room, nestled between four beam engines each 10 million in length, an octagonal atrium of ornately painted cast-iron has been recently restored by Purcell architects. White lilies bloom from golden vines between red columns topped with green acanthus leaves. An ornate smoke stack two-thirds the height of Big Ben was sadly demolished in the 1950s, along with the pumping station’s high Mansard roof. I was disappointed to learn that, despite the weather, this was not a “steaming day”, when volunteers in Victorian garb wake Prince Albert, one of four named steam engines, from its long slumber. (Queen Victoria is nearly operational again.) McLaughlin explained that half of the building has been left unrestored for film and TV rentals in need of a Penny Dreadful atmosphere.

Crossness needs the money. Run almost entirely by volunteers, the property is owned by Thames Water, which has little to spare. The company is now nearly £20bn in debt, despite recently raising customers’ bills by more than 30%. When it rains, Bazalgette’s combined system overflows, pouring untreated waste directly into the Thames. A new £5bn “supersewer”, which at 7.2 metres is as wide as three double-decker buses, opened in February 2025, though some experts say it won’t bury London’s poo problem for good. Andy Burnham has vowed to nationalise Thames Water.

The army of Crossness volunteers seem undeterred. At noon, we gathered for a demonstration beside displays of historical toilet paper (corn cobs, sea sponges, copies of the Daily Express) and loos (antique chamber pots and an 1880s water closet designed by Thomas Crapper). “Come put the pee in Peckham,” a man named Ian said to a young boy in the crowd, “and the water in Waterloo!” The boy tipped a pitcher over into two funnels embedded in a wooden table decorated with a map of London. As we watched the water trickle into plastic tubes beneath the table, Ian explained that Bazalgette’s tunnels decline at such a slight grade that the sewage can travel 16 miles on gravity alone. Then, at Crossness – and here Ian began pumping a plastic accordion hose – steam engines would suck it back up above the level of high tide. Water spat out into a plastic bucket representing the Crossness reservoir. The boy seemed pleased.

Tom Registe, the volunteer manager, tells me proudly that Crossness has just received accreditation from Arts Council England, making it London’s newest museum. “The enthusiasm for sewage is infectious,” he says, before apologising for his choice of phrase.

Illustration by Oscar Ingham for The Observer