On Tuesday morning ITV News went down to the River Chess in Buckinghamshire where Thames Water was letting untreated effluent (liquid waste) flow into the chalk stream.
Water companies have licenses to put sewage into rivers when treatment works reach capacity — the only other option is to let sewage back up into homes. But the licenses only allow them to do this in emergencies, for example when treatment works are overwhelmed by floods.
It did rain heavily on Monday night, hence the discharge, Thames Water told us. But so far this year, the company has run sewage into the river on 96 separate occasions according to local campaigners.