The United Arab Emirates has quit the Opec oil cartel after 60 years of membership, in a heavy blow to the group and its de facto leader, Saudi Arabia, as global energy markets contend with the biggest supply crisis in history. The shock loss of the UAE, Opec’s third-largest oil producer, is expected to weaken the group, which for decades has worked together to use its collective oil production to influence global oil market prices. The UAE’s exit from Opec represents a win for Donald Trump , who has previously accused the organisation of “ripping off the rest of the world” by artificially inflating oil prices by holding back production. Last week Trump confirmed that the US had discussed extending a financial lifeline to the UAE under which the two countries’ central banks could agree to exchange equivalent amounts of each other’s currency should the Middle East crisis deepen.…