When Sir Keir Starmer became Labour leader in 2020, few ever believed he would become prime minister. The party was reeling from its worst performance at the ballot box since 1935, riven by internal divisions, under fire over its record of tackling antisemitism and facing an seemingly unassailable Boris Johnson atop an 80-seat majority. Sir Keir was billed as the Neil Kinnock of 21st-century Labour: the man who would do the hard yards of rehabilitation to get Labour back into the running for whoever came next. But an extraordinary set of events changed all of that: a global COVID pandemic,...