Just 18 months ago, Labour Party activists were despondent at losing the 2015 general election. “The Blairites, in particular,” writes Nunns, “saw the defeat as an opportunity to launch a counter-revolution and reclaim the party. But there was no appetite for a return to a political project scarred by the financial crash, privatisation and war.”

In fact, restiveness in the party had begun under Ed Miliband. The optimism around his election in 2010, when tens of thousands of new members joined, faded as his radical ideas were boxed in by the acceptance of austerity-lite by Ed Balls’ Shadow Treasury team, angering many union leaders who wanted a more hopeful message. But with the Blairites’ vice-like grip over the party’s organisation now weakening, the unions were able to push for more leftwing parliamentary candidates ahead of the 2015 election.

Ironically, it was a push back against this trend that gave the party its new method for selecting a leader. Under pressure from the rightwing Progress faction, Ed Miliband junked the electoral college – an “act of real leadership,” enthused Tony Blair. But the abolition of the MPs’ decisive one-third share of the vote in a leadership election would later operate to Jeremy Corbyn’s advantage. By then, impotent Blairites were disowning the reform they had championed, blaming it all on Ed Miliband.

The post-2015 Blairite narrative, that Labour had lost the election because it was too leftwing, quickly disintegrated. Labour canvassers felt instinctively it was wrong and subsequent academic research proved them right. Above all, it couldn’t explain Labour’s wipe-out in Scotland. A more telling reason for Labour’s defeat was that a majority of voters no longer knew what the party stood for.

Given the state of the organised left in the party in 2015, especially the Campaign for Labour Party Democracy and Labour Representation Committee, many felt pessimistic about the prospects of a leftwing leadership candidate. But there were weaknesses on the other side too. “The prizing of conformity over talent,” observes Nunns, “had produced a lesser quality of MP, reflected in the clutch of mediocre hopefuls initially vying to replace Miliband.” Ultimately the combination of new blood demanding an anti-austerity candidate and a burgeoning online campaign began to reshape the political landscape. When favourite Chuka Umunna pulled out and soft-left hopeful Andy Burnham lurched to the right, a yawning gap opened up for a real leftwing alternative. Step forward Jeremy Corbyn, a man of principle but with virtually no political enemies.

The story of how Corbyn got the necessary nominations just in time is grippingly told, culminating in John McDonnell going down on his knees to beg the last few reluctant MPs to sign up.

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