F or more than a decade, Britain’s acrimonious politics has included a fundamental but often misunderstood battle. Sometimes it is fought out in the open and sometimes more in the shadows. Its protagonists extend far beyond Westminster, into the media, big business, the civil service, activist movements and important but neglected parts of the electorate. And despite how long the battle has been going on, it’s still hard to say which side will prevail. On one side are millions of left-leaning Britons – many of them young – whose economic prospects are worsening, whose anxieties about the climate crisis are rising, whose horror at Israel and the US’s wars is absolute, and whose alienation from the compromises of conventional Labour politics is deep. This is the large minority of the electorate attracted by Jeremy Corbyn’s attempt to radicalise Labour between 2015 and 2019, and now increasingly drawn to Zack Polanski’s leftwing, populist reshaping of the Greens .…