London 'Fatberg' weighing 15 TONNES found blocking sewers Repugnant mass of congealed rotting fat and other sickening waste found Sewage workers have never seen the likes of the mass - as big as a bus It could have sent sewage surging onto the streets of south London A lump of fat the size of a double decker bus has been discovered clogging a London sewer. The Fatberg, described as 15 tonnes of festering food mixed with wet wipes and a host of other disgusting ephemera, was found blocking pipes under Kingston in south London. The revolting mass caused sewage flows through the pipes to be reduced to five per cent of normal capacity and was created by people pouring cooking oils down the drain and flushing sanitary products. Screen grab from CCTV footage of a giant 'fatberg' discovered in a sewer under the streets of Kingston in south London. It was described as the size of a double decker bus The blockage was so critical it threatened to blast untreated sewage through manhole covers onto the streets of one of the leafiest London boroughs. Engineers who found the colossal blockage of congealed fat said they had never seen anything like it. Gordon Hailwood, waste contracts supervisor for Thames Water said: 'We've never seen a single, congealed lump of lard this big clogging our sewers before. 'Given we've got the biggest sewers and this is the biggest fatberg we've encountered, we reckon it has to be the biggest such 'berg' in British history. Rivers of filth: If workers hadn't cleared the mass, raw sewage could have spurted out of manholes across the whole of Kingston The sewer was almost completely clogged with over 15 tonnes of fat. 'If we hadn't discovered it in time, raw sewage could have started spurting out of manholes across the whole of Kingston.' The blockage was discovered after residents in nearby flats complained they couldn't flush their toilets and repairs could take six weeks to complete. Workmen used a high-pressure jet of water to blast away the massive blockage over 10 nights. Mr Hailwood said homes and businesses need to change their ways, and when it comes to fat and wipes people need to 'bin it, not block it'.