IN MAY 2014, the Green Party was in celebration mode. In that year’s local elections, the Greens made 18 net gains. At the time, this was the party’s second most successful set of local elections in its history.

Twelve months later, the 2015 general election would see over one million people vote Green, more than at any election before or since. While record-breaking, that election was bittersweet.

The Greens only managed to retain their sole MP, failing to make further inroads. And within months the position of the Greens as the only mainstream party offering a left-wing diagnosis of the crises facing the country was thrown into doubt by the arrival of Jeremy Corbyn, the most radical leader the Labour Party has ever elected.