Andy Burnham knows all about taking risks and fighting a by-election where victory is uncertain, so he should congratulate Zack Polanski for seizing his moment. Instead, I suspect he will be cursing Keir Starmer for laying the Labour Party open to the possibility of a disastrous defeat. Polanski has put himself forward for selection as the Green Party candidate in the former prime minister’s former seat, Holborn and St Pancras. It is a gamble that will make or break his career, and the prospects of the Green Party for the rest of this parliament. The odds are against him –...