The UK is going to have a new prime minister, possibly by 17 July if no leadership contest takes place. Less than a month is hardly adequate time for Keir Starmer’s successor, who seems certain to be Andy Burnham, to prepare. If Burnham does end up taking up the premiership uncontested, he needs to understand the particular challenges that prime ministers face when transitioning into government mid-term, and use that understanding to guide how he prioritises his own preparation.