Inside London's super sewer: Keeping raw sewage out of the Thames

London’s new super sewer is a monstrous concrete pipe that runs roughly along the course of the River Thames, from Acton to Beckton, 25 kilometres in total. It is designed to solve a problem that London and many other cities have been grappling with for decades – the discharge of raw sewage into the river. In around a year, the project will be complete. The lights will be removed, the access shafts capped, and the tunnel plunged into lonely darkness for at least 120 years. It is possible that we are among the last people to set foot in it.