Oil prices plunged to the lowest level in a week on Monday night as Iran launched a missile strike on a US military base in Qatar. Brent crude fell by as much as 7.6pc to $71.15 a barrel in response to the retaliatory attacks, which were less severe than traders had expected.

U.S. sanctions have barely put a dent on China's massive purchases of discounted Iranian oil, thanks to a shadow supply chain of transshipment.