Why are victims of a Brazil dam disaster suing miner BHP in a London court?

Cacique Bayara, leader of the Pataxo Geru-Tucuna village in the municipality of Acucena in Minas Gerais, wears a T-shirt with an image of her son, Thiago, who died as a result of the 2015 collapse of the Mariana dam in Brazil, stands outside the Rolls Building of the High Court, with Gelvana Rodrigues [Jaimi Joy/Reuters]

Global mining giant BHP faces billions of dollars in potential damages payouts over Brazil’s worst environmental disaster nine years ago, as the first hearing in the much-delayed lawsuit opened in a London court on Monday.

On November 5, 2015, a tailings dam collapsed releasing iron ore sludge into the Rio Doce (Sweet River) in southeastern Brazil. The toxic waste contaminated the river water and damaged its ecosystem. The mining waste washed away the nearby Bento Rodrigues village, killing at least 19 people.