Rio Tinto awarded hugely profitable iron ore contracts to the key witness in the bribery trial of four Rio executives in March 2010, weeks before he was due to testify about his corrupt payments to the mining giant’s marketing executives.

The contracts helped Du Shuanghua, the head of Rizhao Steel Corporation, report a $US160 million profit in the first six months of 2010 from a Singapore marketing hub he had just set up — and higher earnings would follow.