In Parliament, Mr. Burnham’s record was strikingly loyalist. He voted for the Iraq war and, as a junior Home Office minister, took a tough approach to law and order. At the time, he was known in Westminster as Flog ’em and Burnham. Promoted to the cabinet under Gordon Brown, he pushed along New Labour’s ruinously expensive program to rebuild hospitals with private financing.

His ambitions, however, were bigger. When Labour was ejected from office in 2010, Mr. Burnham stood for party leader on a word salad of “aspirational socialism” and finished fourth. He ran again in 2015 as the bookmakers’ favorite, only to lose after the surprise surge of support for Jeremy Corbyn. Two years later, he found an election he could win closer to home, becoming the inaugural mayor of Greater Manchester.

The mayoralty comes with few powers. Its chief functions, according to the Oxford Economics consultancy, are “to argue for the region” and provide “a point of contact for private investors.” Mr. Burnham had found his level. The wider city-region, which has a population of 2.9 million, has recorded stronger growth than Britain’s other conurbations. Disposable incomes haven’t grown by much, though, and house-price inflation has left many residents behind. Still, there’s enough construction activity and service-sector buzz to call it a success story.

Mr. Burnham claims to have found a secret economic sauce, “business-friendly socialism,” or just plain “Manchesterism.” Yet his mayoralty will be chiefly remembered for two things: taking buses back under public control, which he had to be talked into, and his furious off-the-cuff reaction in 2020 to tougher lockdown restrictions imposed by the Boris Johnson government. Mr. Burnham thundered at how Westminster was “grinding people down.” For his impromptu defiance, the media gave him that “King of the North” epithet.

Yet the appellation wasn’t so much plucked from the ether as lab-grown by the man himself. Speaking at an event earlier that year, Mr. Burnham had daydreamed about “sitting in my ‘Game of Thrones’-type castle at the heart of the dominant Northern Powerhouse, opening my birthday telegram from the monarch of the south of England.” A Labour ally took his cue, joking that “Andy’s going be on the Iron Throne and King of the North.” The Manchester Evening News duly ran the headline.