Calling the oil market has been as slippery a job as the black stuff itself of late, and so it proved today. US President Donald Trump put a rocket under the oil price yesterday, tweeting that he had brokered a deal between Russia and Saudi Arabia to cut output. Today those gains were initially trimmed amid fears Trump wouldn’t make his promise stick, but chatter that the Opec oil cartel might meet next week helped lift Brent Crude up $1.11 to $31.03. Shares in BP and Shell both fell, down 8p to 345p and 27p to 1515p respectively.