A tanker traveling off the coast of Oman in the Strait of Hormuz caught on fire early this morning after being struck by a projectile, the British military said.The attack was the latest targeting a vessel moving through the narrow mouth of the Persian Gulf, through which a fifth of all oil and natural gas traded once passed in peacetime.The US is in negotiations with Iran aimed at fully reopening the strait, rolling back Tehran’s nuclear programme and reaching a permanent end to the war it began with Israel on February 28.