When people think of London's river, they think of the Thames. But the city was built around many other rivers too - and traces of these still remain for those who know where to look.
A secret network of underground rivers snakes beneath the capital. The rivers predate the city and its people. The rivers may be buried, but they still flow underground. In some places they can be seen and heard.
By rediscovering them, and tracing their courses, the way we see London is transformed. Using the visual and aural clues left in the streetscape, we can burrow down through layers of London history to river level, revealing the city as it once was.
Tom Bolton is a researcher and writer, the author of London's Lost Rivers: A Walker's Guide: a series of ten walks tracing these hidden routes across London published by Strange Attractor.