Mining and commodities giant Glencore Xstrata announced Thursday that it had made former BP chief Tony Hayward's interim stint as company chairman permanent. "The board is very pleased to announce the appointment of Tony as permanent chairman, following an extensive search process," Peter Grauer, head of the Swiss company's nomination committee, said in a statement. Hayward, who quit as head of energy giant BP in the wake of the April, 2010 Deepwater Horizon oil rig spill in the Gulf of Mexico, has been serving as interim chairman since Glencore and Xstrata's mega merger a year ago. "Over the last twelve months, Tony has provided exemplary leadership of the board and proved himself to be the outstanding candidate to take on the role permanently," Thursday's statement said, adding that Hayward would take on the role "with immediate effect." Hayward was vilified in the United States after trying to downplay the environmental impact of the BP-leased Deepwater Horizon rig explosion, which killed 11 workers and caused millions of barrels of oil to spew into the sea. He joined commodities trader Glencore International's board a year after the spill, before the company, which has since merged, went public.