The slowing world economy is not strong enough to handle an oil supply shock.

At this juncture it would trigger a full-blown slump. Yet that is exactly what we risk as Donald Trump tries to drive every last barrel of Iranian crude oil off the global market.

A spike in Brent oil to $120 by early next year would probably be enough to tip the eurozone and Japan into recession, and would be the coup de grace for large parts of the emerging market nexus.

It would amplify the effects of monetary tightening by the US Federal Reserve and the European Central Bank already in the pipeline, and which will hit with full force in the first quarter of 2019.

The likelihood of such an oil spike has risen from implausible to near 50:50 as it becomes clear that the Trump administration really does intend to knock out 2m barrels a day (b/d) of Iranian exports by early next year. Those barrels are the difference between ample world supply and an almighty crunch.

Mr Trump is likely to get his way. The evidence so far is that not even China National Petroleum Corporation and Sinopec dare defy Washington. China’s giant refiners have notified Tehran that they will stop buying Iranian exports after the sanctions deadline passes on Sunday. So has India’s Reliance.