New York

Opec is back in the business of influencing oil prices as Saudi Arabia works with Russia and Iran to limit output, and only "a brave person" would bet against this, oil bull Andy Hall said in his latest investor letter.

The hedge fund manager is up nearly 18 per cent for the year at his US$2.5 billion Astenbeck Capital Management in Southport, Connecticut, after his fund rose 6 per cent in September as oil rallied.