Editorial: The prime minister's brutal clearout of his predecessor's cabinet has shown he can wield the knife. Now, he must prove he can chart a different course for Britain

Andy Burnham faces a daunting in-tray as Britain’s new prime minister, from a slowing economy and strained services to volatile global crises and US ties.

Andy Burnham takes office as Britain's prime minister Monday, facing mounting pressure to tackle the political and economic challenges that have...