British multinational Shell continued operating a major oil pipeline in Nigeria for years even though it knew it was causing widespread pollution - despite a warning from its own staff and its own technical standards, internal documents obtained by the BBC show. Across Nigeria's oil-rich southern Niger Delta, decades of oil spills have left a landscape deeply scarred, with wetlands increasingly coated in crude and contaminated sediment. In court papers the oil firm argues that most of the pollution has been caused by "large-scale oil theft, sabotage" and dozens of illegal refineries, and that its Nigerian subsidiary invested heavily over many years to reduce the risk of and response to spills. Tap the link in @BBCNews's bio for more. #Nigeria #Shell #BBCNews