Last week saw Opec, Russia and their associates congratulate themselves on an extension of their ‘historic’ output deal to end-2018. It also saw US crude output top 9.7mn b/d for the first time since 1970.

Saudi Energy Minister Khalid al-Falih insists that the default for the Opec/non Opec deal extension, agreed in Vienna 30 November, is that it will run right until the end of 2018. If so, Opec faces a long year ahead. If Opec and the 10 non-Opec hangers-on succeed in sticking...