The subterranean rivers of London are the tributaries of the River Thames that were built during the growth of the famous city. They flow through underground culverts, with a number of them now integral parts of London’s sewage system. The River Fleet is the largest of these, its headwaters are two streams on Hampstead Heath, each of which were dammed into a series of ponds in the 18th century.
And this underground labyrinth, which joins at Camden Town, was explored by presenter Dallas Campbell during the BBC’s ‘Secret Sewer River of London – World Beneath Your Feet’.
He said: “It looks like a sewer and smells like a sewer because it is a sewer.
“Back in the early 19th century, the open River Fleet was essentially a cesspit carrying disease through London so it was decided to cover it up and using 318 million bricks.
“Victorian engineers turned it this – it means that millions of us can now live without the risk of disease in a few square miles.
“But it also hides some pretty gruesome surprises.
“Dave Dennis is one of an army of underground workers that keep the fleet flowing – surely one of the least enviable jobs in Britain.”
Due to poor environmental conditions and what we would now consider to be basic sanitation, there were several devastating outbreaks of diseases in Victorian Britain.
As a consequence, our predecessors had to take drastic measures to protect residents.
But today, thanks to a breakthrough in engineering, it is the job of Mr Dennis to manage the four kilometres of sewage water flowing beneath London.
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“We have to come down and break it up so it’s okay to flow downstream.
“This is a fatberg, look at the worms in it.”
And Mr Campbell confirmed he would not want to return.
He said in 2016: “When you guys say ‘don’t pour fat down your sink,’ you actually mean it.
“What begins as an innocent bit of grease in your kitchen can quickly transform into a fatberg.
“This is a job I don’t want to repeat anytime soon.”
The river gives its name to Fleet Street, the eastern end of which is at what was the crossing over the river known as Fleet Bridge and is now the site of Ludgate Circus.
The Fleet rises on Hampstead Heath as two sources, which flow on the surface as the Hampstead Ponds and the Highgate Ponds.
They then go underground, pass under Kentish Town, join in Camden Town, and flow onwards towards St Pancras Old Church, which was sited on the river’s banks.
It then follows King’s Cross Road and other streets, including Farringdon Road and Farringdon Street.
The valley then broadens out and straightens, to join the Thames beneath Blackfriars Bridge.