In two months, Telegraph deputy editor Rob Winnett will leave London, where he has spent a lifetime burnishing his credentials as a tireless, scoop-hungry journalist, and move to America to become top editor of The Washington Post—the head of the paper’s “first newsroom” in evolving Post parlance. In media circles on his side of the pond, this is seen as significant news. Winnett, after all, is a minor legend on Fleet Street—a soft-spoken but ruthlessly determined newsman who led The Telegraph’s explosive investigation into the U.K. parliamentary expenses scandal and earned the sobriquet “Rat Boy” along the way. “He is highly regarded and thought of as the engine in the newsroom,” one veteran British media executive told me. For The Telegraph, this person said, “it is a big loss.”