If Andrew Mackenzie thought he was facing a career-defining moment, his mood betrayed none of it on Tuesday as he delivered perhaps the most important profit result in BHP's recent history.

"We did foresee many if not all of these trends some time ago," the BHP Billiton chief executive said of the plunging commodity prices that wreaked havoc on the miner's first-half profits and led to its dividend being brutally slashed.