LONDON — Britain woke Friday to the scene of a political earthquake. The opposition Labour Party, after 14 years in the political wilderness, has handed a brutal defeat to the ruling Conservatives. Party leader Keir Starmer is now certain to become prime minister in the coming hours, replacing his Conservative Party counterpart, Rishi Sunak, who has presided over one of the worst electoral losses in British political history. “We did it,” Starmer told a cheering crowd in an early-morning speech in central London. “You voted for it and now it has arrived. Change begins now.” He thanked voters, saying they...