Sir Keir Starmer insists he will go on but even those cabinet colleagues who have publicly declared their support for him know that his authority is shattered. The prime minister, so assured after winning a landslide general election victory in July 2024 that he was contemplating at least a decade in power, has in less than two years become an embarrassment to Labour and an electoral asset to his opponents. Starmer’s old assurance of power will never return. If he continues in office for a while longer — perhaps until the autumn, perhaps even into next year — it will...