In physical terms, Mr. Gordon Brown has not gone far this week: He moved his office one door down, from No. 11 to No. 10 on Downing Street in London. He did not even have to move his family, which already lives at the private quarters at No. 10. But the change in jobs from chancellor of the Exchequer (finance minister) to prime minister signals the beginning of a new era for his country.

Mr. Brown now faces the challenge of his lifetime: He must rejuvenate a government and a Labour Party that have been battered by the war in Iraq and build on the political record of his predecessor, Mr. Tony Blair.

Mr. Brown has long toiled in Mr. Blair's shadow. The two men joined Parliament in 1983 and forged an intellectual partnership that transformed their Labour Party. They allegedly cut a deal in 1994 that acknowledged that Mr. Blair was the more electable leader of the two.