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

The mining giant faces a potential $47bn lawsuit filed by at least 600,000 people over the 2015 mining disaster.

Why are victims of a Brazil dam disaster suing miner BHP in a London court?
The mining giant faces a potential $47bn lawsuit filed by at least 600,000 people over the 2015 mining disaster.