LONDON (Reuters) - Britain is in the midst of its deepest downturn in peacetime as the coronavirus pandemic wreaks havoc on the economy, a Reuters poll of economists found, while an expected recovery in the second half is already in jeopardy.The coronavirus has swept across the world, infecting more than 2.5 million people and killing over 177,000, forcing governments to impose strict lockdowns and shutter industries while pushing central banks to unleash unparalleled stimulus.Britain closed up..