Keir Starmer was meant to fix the country, having promised a clean break from the chaos which engulfed the Conservatives. But on Monday, less than two years after his landslide win, the prime minister acknowledged he no longer has the support of his Labour MPs and would stand down in weeks. His announcement means the UK is now, remarkably, heading for its seventh PM – all-but certainly Andy Burnham – in a decade after years of alarming churn in Downing Street.