For the last four UK general elections, bar 2015, the 10pm exit poll on election day has been almost exactly correct, even if sometimes the predictions have been a shock to many experts. So the likelihood is that the pollsters have got it right again in 2019. But whereas in 2017 their correct prediction of a hung parliament guaranteed a embattled legislature, the 2019 prediction may even transform British politics.

The Jeremy Corbyn project has taken what is surely a terminal beating

This election looks to be a triumph for the Conservatives under Boris Johnson. Their strategy of calling an early election and their campaign and messaging tactics during the last few weeks has been vindicated, with a predicted 368 seats in the new parliament, a majority of 86 over all other parties, and an incontrovertible mandate to take the UK out of the European Union in January.

If the exit poll is even broadly right, the message for the Tory party is of an historic recovery after the humiliations of the New Labour era. It transforms all recent analysis of the party’s place in UK politics, reuniting it with its reputation as the most resilient and successful election-winning party in Europe. The party has not won a comfortable working majority since 1987. A majority of 86 would mean Johnson can govern for a full five-year term, even though his promise to repeal the Fixed-Term Parliaments Act means he is likely not to take the country into another December election in 2024.

The victory is undeniably Johnson’s. A year ago he was on the backbenches. A majority of Tory MPs did not want him as their leader in the summer. Now he is the master of the British political scene, and will be able to pick his own cabinet, demand his MPs’ backing for his Brexit strategy (which may differ significantly from the one he has led his party to expect). He now has little reason to worry about Nigel Farage’s Brexit party either.

Facebook Twitter Pinterest A Conservative party supporter pictured shortly after the BBC’s exit poll. Photograph: Tolga Akmen/AFP via Getty Images

The question is whether this apparently emphatic victory is about “getting Brexit done” or whether it is a wider endorsement of Johnsonian Conservatism. The night’s detailed results will do much to supply the answer to this question. But if this is a Brexit victory, it may – possibly – prove in the end to be pyrrhic. If Johnson delivers Brexit and the Labour party reorganises, their position may prove a more fragile one than it seems immediately.

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The second huge message of this election is that the Scottish National party has received a mandate – with a projected 55 seats in Scotland – to press for a second referendum on independence. Johnson has made clear he will not do what David Cameron did and concede a second indyref poll. His mandate is to defy the SNP. But the SNP has been prepared for this fight for months. The confrontation in Scotland will be at the very top of the political agenda now.

The final big message is Labour’s epochal collapse. Labour has lost four general elections in a row. Its projected 191 seats is its lowest in modern times. The Jeremy Corbyn project has taken what is surely a terminal beating. But the Liberal Democrats have not prospered at Labour’s expense. That achievement belongs to the Tories. Corbynites will doubtless blame everyone but themselves for this total disaster. But the question on the left of British politics is now the one that was embodied in the title of a book published after the last time Labour lost four elections in a row in 1992. The title was: Labour’s Last Chance? And one of the editors was John Curtice, whose exit poll this evening now poses that self-same question once again, nearly 30 years on.

• Martin Kettle is a Guardian columnist