Another day, another record high in international oil prices. West Texas Intermediate, the US benchmark crude, has hit by some measures its highest ever price in real terms. Its relentless surge poses a conundrum for Opec, the oil producers’ cartel, which meets on Wednesday in Vienna to review output quotas.

Yet member states, to the disappointment of consuming nations, are not discussing a quota increase to damp prices. Instead, they are expected either to cut oil production or to keep to their existing limits.