The River Fleet rises on Hampstead Heath and runs buried under London to the Thames. A guide to Hampstead's lost rivers, their source ponds and how to trace them.
The Lost Rivers of Hampstead: Following the Fleet Underground
Most people who walk past the ponds on Hampstead Heath have no idea they are looking at the source of a river. The chain of ponds you see is the beginning of the River Fleet, which once ran openly down through Kentish Town and Camden to the Thames at Blackfriars. London buried it. The river is still there, flowing under the streets, but you cannot see it any more. This is the story of where it starts and how to trace its path on foot.
Where the Fleet begins
The Fleet has two arms, and both rise on the high ground around Hampstead. One starts in the ponds on Hampstead Heath proper, the chain that includes the bathing ponds at the Highgate end. The other rises in the Vale of Health pond and the ponds on the western side. The whole area sits on a layer of sand over clay, which is why there are so many springs here, and it is also why Hampstead became a spa town in the eighteenth century. People came to drink the water.
Stand at the southern end of the Hampstead ponds, near South End Green, and you are roughly at the point where the open river used to head off toward the city. From here on, it is underground.
Why it disappeared
The Fleet was a real river, wide enough near the Thames to carry boats. By the seventeenth century it had also become an open sewer, which is what happens to a city river that everyone uses as a drain. After the Great Fire of 1666 there was an attempt to clean it up and turn the lower stretch into a proper canal. That failed. The water was too filthy and the trade never came.
So London did what it kept doing with its smaller rivers: it covered them over and turned them into part of the sewer network. The lower Fleet went under in stages through the eighteenth century. By the mid-nineteenth century it had become part of Joseph Bazalgette's great sewer system, which is broadly where it still sits today.
You cannot follow the actual river, but you can follow the valley it cut, and the street names give it away. Here is a walk that traces the line from the source toward Camden.
- Start at the Hampstead Heath ponds and walk down to South End Green.
- Follow the dip down Fleet Road, which is named for the river and sits in its old valley.
- Continue toward Gospel Oak and Kentish Town, staying in the low ground where the water would have run.
- By Camden you are on the line where the two arms of the Fleet joined.
The trick to spotting a lost river is to watch the gradient. Roads that dip and then climb are often crossing a buried valley. Once you start noticing it, you cannot stop.
The clues above ground
There are a few places where the Fleet leaves a mark you can actually see. Street names are the obvious one: Fleet Road, Anglers Lane in Kentish Town (named for people who once fished the river), and of course Fleet Street itself near the Thames, which marks the river's mouth. The famous Bagnigge Wells, a pleasure garden near King's Cross, was built around the Fleet's water.
If you put your ear to a drain cover in the right spot near Kings Cross or Farringdon after heavy rain, people say you can hear water moving below. I have tried this and convinced myself I heard it, which is not the same as actually hearing it. Believe what you like.
The other Hampstead rivers
The Fleet is the big one, but it is not alone. The Westbourne, which surfaces briefly as the Serpentine in Hyde Park, draws part of its water from the high ground to the west of Hampstead. The Tyburn also rises in this band of springy hills. Hampstead and the ridge it sits on feed several of London's hidden rivers, which is one of the reasons the area has always had so much water and so many wells.
Why this is worth knowing
It changes how you see the Heath. The ponds are not just pretty water features that someone landscaped. They are the dammed headwaters of a real river, and the reason Hampstead exists as a place at all has a lot to do with that water: the springs, the spa, the wells that drew people up the hill. Once you know the Fleet is down there, the whole layout of the land starts to make sense.
Frequently asked questions
Where does the River Fleet start?
The Fleet rises from springs on Hampstead Heath and the high ground around Hampstead. The ponds on the Heath, including the bathing ponds, are its source, and a second arm rises near the Vale of Health.
Can you still see the River Fleet?
Not in central London. The Fleet runs underground as part of the sewer network from Hampstead down to the Thames at Blackfriars. The closest you get to seeing it openly is the chain of ponds on Hampstead Heath, which are its headwaters.
Why was the River Fleet buried?
By the seventeenth century the lower Fleet had become an open sewer. Attempts to clean it and make it navigable failed, so London covered it over in stages and eventually folded it into Bazalgette's Victorian sewer system.
How do you trace a lost river in London?
Follow the low ground and watch for street names. Roads that dip into a valley and climb out the other side often mark a buried river. Fleet Road in Hampstead is a clear example, sitting in the old valley of the Fleet.
