Fighting 'fatbergs' with the chief flusher of London
A marvel of Victorian engineering, London's sewers were built after the deaths of 10,000 people in 1853 and the "Great Stink" five years later.
And their creation meant a separation of Londoners and their waste, both moving around the city in separate but connected worlds.
Reminders of this subterranean world arise only when something goes wrong, or when sewer staff find something extraordinary.
Earlier this year, Thames Water came across a 15-tonne mass of fat and waste products in Kingston-upon-Thames. The size of a double-decker bus, this congealed clot of waste was the largest "fatberg" ever discovered in Britain.
A BBC crew headed underground to meet the people who tackle "fatbergs" and keep the city's sewerage network flowing.Continue reading the main story
Photographs and slideshow production by Laurence Cawley.