Russia extended its lead over Saudi Arabia as top crude supplier to China to six straight months in August. Russia supplied 1.046mn b/d, whilst Saudi Arabia – near-undisputed number one as recently as 2015 – supplied just 861,000 b/d. On a three-month-moving-average basis Saudi supplies are at their lowest level since early 2014. Indeed for five of the last six months, including August (977,000 b/d), rival Opec producer Angola has bested Saudi for second place.

But not only are...