In 1993, just after Labour had suffered its fourth successive election defeat, David Hare wrote a play called The Absence of War. It was about the party, about British socialism, but really it was about the torture of trying to be liked while suspecting you’re unlikable. As research, Hare had been granted rare access to Neil Kinnock, and his fictional party leader, George Jones, is just as warm and garrulous and politically agonised.

He can never say what he really believes for fear of polling badly. Not a whisper about tax rises. No deviation from the market-tested script written for him by the aides and consultants. He fools no one. As his shadow chancellor says: “It’s not that the party don’t believe in you, you know. I say this in love. They smell that you don’t believe in yourself.”

Hare’s portrait sums up most of the Labour leaders I’ve known: Kinnock, Gordon Brown, Ed Miliband – compassionate, intelligent and thoroughly uncomfortable in their own skins. Each convinced that if the public saw their true political nature they’d lose that election that they ended up losing anyway.

One mark of Jeremy Corbyn’s success last night is he did what he did with none of that. No triangulation. No disavowal of the s-word. None of the soft racism previously mandatory in mainstream politics.

Corbyn went to war on a manifesto that was the breeziest defence of European social democracy I’ve seen in my adulthood. He faced down two years of coup attempts from his own parliamentary party and aerial bombardment from the rightwing press (on the eve of polling, Paul Dacre devoted the first 18 pages of the Daily Mail to claiming that Corbyn, John McDonnell and Diane Abbott were all terrorist-lovers). He responded with a mass campaign and two fingers to most of the press. In the process an election that started out as a foregone conclusion turned into one of the biggest political upsets ever seen in postwar Britain.

And that’s just one of the ways in which Corbyn and his team last night changed British politics for good.

We can rattle off a few of the others: the previously insuperable Theresa May is now toast. May in 2017 will go down as the most disastrous Conservative leader since, well, David Cameron in 2016: both prime ministers who staked everything on a punt to increase their power – only to find their power taken off them by the voters.

Britain probably won’t have to go through the gigantic self-harm of hard Brexit. Indeed, given that the next couple of years now holds more leadership contests and general elections, it’s not clear to me how any government can complete the article 50 negotiations in time.

What’s clear is this: Corbyn and his team have just upended most of the rules of British electoral politics. For most of my life, politics has been presented as a set of questions to which all serious people knew the answers. You let south Wales and the north-east go to hell, while allowing the City to do whatever it wants. You agree that the public realm is important, while sighing that it’s just too expensive to keep up. When things go wrong you bash a few immigrants. And you always, but always, keep to the political centre ground – as if that were a destination you could plug into Google Maps.

After last night, you can’t claim that any more. The rules followed in The Absence of War no longer work so reliably.

We’ve entered a political era in which authenticity is the No 1 quality – that is the thing that binds Corbyn to Boris Johnson to Nigel Farage, and which May and Cameron conspicuously lack. After seven years, the public is exhausted with austerity – just see how quickly the terror attacks turned into an argument over police funding. After decades of being told they can’t have the basics for secure livelihoods, the voters have decided they want them anyway.

In fairness to May and her team, they grasped some of that while being unable to reconcile it with post-Thatcherite Conservatism. But it was Corbyn and his team who’d best worked out some of the answers. And most of them revolve around one thing: British social democracy is back.

Hare’s play ends in yet another Labour defeat and the dejected Jones musing: “Is this history? Is everything history? Could we have done more? Was it possible? And how shall we know?”

Last night, we got an answer.