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. The files, including emails and presentations, reveal that a senior Shell executive cautioned as early as 2008 about the risks of continuing to pump millions of barrels of unrefined fuel through one of the company's main pipelines in Africa's biggest oil producer while it was subject to massive and destructive uncontrolled theft and infrastructure failures. 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. The BBC obtained the internal documents after Shell disclosed them as part of ongoing legal proceedings in the UK brought by communities living around the creeks and mangroves of the Niger Delta, who want Shell to be liable for the pollution caused by more than 100 leaks stemming from theft and illegal refining of oil between 2011 and 2013 that have damaged their health, environment and livelihoods. The 60-mile (96.5km) Nembe Creek Trunk Line runs near the riverine community of Bille, which is made up of 45 islands, from inland oilfields to a coastal processing site for exporting.