What the hell just happened? The Guardian’s Richard Adams attempts to make sense of the shock UK election outcome.

The UK election result is the biggest upset of conventional wisdom since, well, last November. After Trump, the Brexit referendum, Leicester City winning the premier league and the 2015 UK general election result you’d think we’d be getting used to this. But no.

The Conservative party’s decision to call a snap election has backfired: rather than winning the comfortable-to-huge majority predicted, the Tories have instead gone backwards. The party has held enough seats to govern in coalition with Northern Ireland’s Democratic Unionist party but it was a miserable effort in almost every other respect.

Nervous and ill-advised, Theresa May achieved the unthinkable: winning more than 42% of the popular vote but losing a swathe of seats in England. (In 2005 Tony Blair won 35% of the vote but a solid majority of MPs.) Labour under Jeremy Corbyn got around 40% and gained more than 30 seats. The Tories piled up wasted votes in safe seats and failed to go beyond their comfort zone to win votes in London and the east of England. And that in a nutshell is why May lost as she did.

Why did the Tories do so badly in its England heartland? Brexit – the referendum to leave the European Union – hung over this election like an embarrassing smell. The UK Independent Party (UKIP) collapsed as predicted, having won the EU exit it sought, but its voters didn’t obediently file back to the Tories as the pundits expected. Enough – perhaps 40% – returned to Labour to make a difference.

And then there was the 18-30 youth vote. Largely pro-Labour but with a poor record of actually voting, this time the youth turned out in higher proportions, with the exact amount as yet unconfirmed. This is a major reason why so many polls got it so wrong: they assumed that voting behaviour wouldn’t change much. But young people appeared more exercised by Brexit and Labour’s policies including the scrapping of student tuition fees that currently stand at £9000 a year.

The pollsters’ performance brings to mind the football pundit Alan Hansen, who once rubbished Manchester United’s chances of winning the English league: “You can’t win anything with kids.” One of those kids was David Beckham, and we know what happened next.

But Labour under Jeremy Corbyn also did better than expected with older voters, thanks in part to returning UKIP voters and perhaps as a result of Theresa May’s overconfident campaign that offered its key base of supporters a “dementia tax” and downgraded pension protection.

The Conservative campaign overall was nightmarish, revolving around May’s “strong and stable” leadership backed by lurid excesses by the Daily Mail, Telegraph and Sun. As tactics go that’s fine but May herself couldn’t carry its weight. She refused to debate with Corbyn, was generally lacklustre and failed to offer any detail about how the Tories planned to negotiate Brexit. The single biggest political issue on the table and May ignored it to concentrate on domestic policies. This played into Labour’s hands, disastrously, by moving debate to Labour’s strengths: spending on health, education and social services.

Then the campaign was twice derailed by two terrorist attacks. The attack in Manchester came just as almost every newspaper was printing front pages deriding May’s “dementia tax” U-turn. They all changed overnight to describe the Manchester carnage.

But the later London Bridge attack may have eroded May’s image of competence. As Home Secretary for five years she had been responsible for policing and domestic security. After London a string of complaints appeared about how the attackers had been allowed to enter and remain in the UK, along with steep cuts in police numbers that also happened on May’s watch.

Although election campaigns rarely have a major effect on final results, the closeness of the UK result suggests too many voters were unimpressed by May and her team. Perhaps convinced by those polls predicting huge Conservative majorities, the Tory strategists played it safe. No hostages to fortune on Brexit, giving themselves plenty of room of taxes, and a readoption of some ancient Tory policies like bringing back fox hunting and grammar schools, when the result indicates that UKIP and potential Labour voters don’t give a damn about either.

The other caveat about election campaigns is that they do help the profile of under-exposed leaders. In that sense the snap election was a relief for Jeremy Corbyn: it halted Labour’s infighting and allowed him to approach the public directly. He was helped, it seems, by the growth of left-wing activism on the web – a Buzzfeed survey of Facebook found that aggressively pro-Corbyn and Labour news was shared far more widely than similar efforts for the Conservatives.

By avoiding Brexit discussion during the campaign, May gave Corbyn an opening that he rushed to fill with populist policies. The Conservatives offered nothing in response apart from slogans about stability and Brexit meaning Brexit. In her one major speech May even claimed that Brexit required a return to grammar schools (that is, schools reserved for the most able children as selected by an exam sat by 11-year-olds). It was, incredibly, perhaps her most concrete policy statement of the election.

Outside of England and Wales – where Labour continued to dominate despite the nation’s huge pro-Brexit vote – the Conservatives did much better. In Scotland the independence issue rivalled Brexit as a vote driver. In 2015 the pro-independence vote flocked to the SNP. This time it seems that the pro-Unionist vote coaleased in response around the Tories, hence their success. The SNP’s meltdown will be one of the election’s major political aftermaths.

But what happens next? Conventional wisdom would go like this: the Tories form a coalition with the DUP of Northern Ireland; May eventually steps down as PM to be replaced by Boris Johnson; the Tories present a populist Budget with tax cuts and NHS funding galore which gets voted down, followed by another snap election in, let’s see, November? February?

But who knows? New Zealanders will recognise that governments can be sustained with slim majorities. The UK did just have five years of coalition government so it’s not so unlikely. We’ll all be finding out a lot more about the DUP, its policies and the foibles of Belfast and Ulster politics. Foxes are probably safe for the time being.

Meanwhile the clock ticks towards Brexit – whatever Brexit means now.

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