Legal fees for the 22-week trial in the class action against mining giant BHP over the 2015 Mariana dam disaster in Brazil could top £350 million ($680 million) as both sides engage in bitter courtroom warfare.

BHP’s portion of the costs are forecast to be about £108 million, according to documents filed with the court. The mining giant, which is dual listed in the United Kingdom and Australia, has storied Magic Circle law firm Slaughter and May defending it, along with a swath of king’s counsels.