FTSE cheers easing U.S.-Iran worries; midcaps miss out

(Reuters) - London's main index advanced on Thursday as chances of a full-blown crisis in the Middle East waned, but the midcaps lagged as SIG and Marks and Spencer fell after warning of lower annual results and dragged their peers lower.The FTSE 100 rose 0.4% and was set for its best day in a week after U.S. President Donald Trump stepped back from more military action against Iran and Tehran signalled an end to retaliation."It looks like the shooting war is over for now, but there is always..