Boris Johnson has broken Britain's deadlock over leaving the European Union with a dramatic election win, but the victory could lead to new and potentially damaging confrontations with both Scotland and Northern Ireland.

Johnson, with his trademark floppy white hair and a reputation for making off-colour remarks, was dismissed by opponents — including many in his own party — as untrustworthy and something of a buffoon. But as the results began trickling in early Friday morning, it was clear his victory had dramatically redrawn the U.K.'s electoral map.

"What happens with elections is if you win, all the sins get washed away. He is at the pinnacle of his power," said conservative commentator Craig Oliver, who served as communications director for former Conservative prime minister David Cameron.

The Conservatives are on track to take at least 364 seats, giving Johnson's party a healthy majority and handing the Labour Party its worst defeat in more than a generation.

"Just utterly devastating," tweeted well-known Labour commentator Owen Jones. "Brexit just smashed us. Keeping together an electoral coalition of 'Remainers' and 'Leavers' as the country bitterly divided just became impossible."

Britain's opposition Labour Party Leader Jeremy Corbyn waits for the General Election results of the Islington North constituency to be announced. His party lost big on Thursday night. (Hannah McKay/Reuters)

Labour Leader Jeremy Corbyn spoke only briefly after being proclaimed the winner in his London riding of Islington North.

In his speech, Corbyn said while he would be stepping down as leader, it might not happen right away. Corbyn suggested he planned to stick around through what could amount to a long transition period.

Labour loses big in longtime strongholds

The Conservatives made deep inroads into traditionally Labour seats, especially in northern England, as the vote appeared to polarize over Brexit.

"I want to thank Boris," said winning Conservative candidate Ian Levy, whose surprise win in Blyth Valley on the northeast coast of England early in the evening signalled the kind of night it would be for Labour.

No Tory had been elected there in almost 80 years.

Nearby in Sedgefield, the seat of former Labour prime minister Tony Blair swung Conservative in a stunning upset. And in Bassetlaw, a previously safe Labour seat near Sheffield, the Labour vote utterly collapsed.

"Brexit had been this dividing issue since the referendum was called, and it seemed that [Brexit] cut across the traditional Labour-Conservative, left-right divide," said Tim Durrant, associate director of the Institute for Government in London.

"People voted in terms of the party's Brexit policy, as opposed to party loyalty."

Scotland 'flatly' rejects Johnson's plan, SNP leader says

But just as vast swaths of rural England turned Conservative blue, Scotland was painted with the yellow colour of the Scottish National Party.

The SNP is on track to win an unprecedented 48 of Scotland's 59 seats — a 13-seat increase. The major gains position Scottish First Minister Nicola Sturgeon as a major voice of opposition as Johnson moves forward with plans to break away from Europe.

Scotland strongly backed the bid to remain in the European Union in the 2016 referendum.

Scottish National Party Leader Nicola Sturgeon celebrates as she hears her party has unseated Britain's Liberal Democrat Leader Jo Swinson. (Andy Buchanan/AFP/Getty Images)

"Boris Johnson's argument to Scotland has been flatly and completely rejected," Sturgeon told the BBC in the early hours of Friday morning.

"There is no doubt that I have a mandate to offer people that choice."

Johnson is on the record as saying he will not agree to another referendum so soon after the last vote in 2014, which sets up an epic confrontation between two leaders with large majorities behind them.

The 2014 referendum on Scottish independence saw 55 per cent of voters cast their ballots to stay in the U.K. That vote was sanctioned by Westminster, whereas a future unsanctioned vote would be legally dubious.

But Johnson, who will face major decisions and negotiations around Brexit even after securing his majority, will be in a difficult position politically if Sturgeon moves toward holding another referendum.

'Northern Ireland is the one to watch'

The other major upset of the night came in Northern Ireland, where parties that favour strong ties with the rest of Britain were overtaken by those with more nationalist leanings.

"Northern Ireland is the one to watch," said Durrant, noting that the election of 11 nationalist MPs there marks the first time ever that so-called unionist parties have been in the minority there.

A voter passes an advertising board featuring an image of the Democratic Unionist Party's deputy leader, Nigel Dodds, as she leaves a polling station in Belfast, Northern Ireland. (Paul Faith/AFP/Getty Images)

"Northern Ireland voted to remain in the EU, and there's been a lot of disappointment in Northern Ireland about the way the DUP (Democratic Unionist Party) supported the Conservative government."

If Scotland votes for a referendum, Durrant said it will no doubt intensify debate in Northern Ireland about whether its future lies inside or outside of the U.K.

'We don't really know him fully,' analyst says

Johnson — a former journalist who has been in or around politics virtually his entire life — has long faced criticism for adopting and then shedding political positions with little apparent intellectual discomfort.

His hard opposition to Europe during the Brexit campaign surprised many Conservatives, as did his intense push over the last few months to take Britain out of the EU without a deal.

Durrant said with a comfortable majority behind him and the need to appeal to all those first-time Conservative voters, Johnson's thinking may evolve yet again.

"The thing with Boris Johnson is that we don't really know him fully," he told CBC News in an interview.

WATCH: See what Boris Johnson had to say Friday after securing a majority

Conservatives win big after campaigning on pro-Brexit message 2:53

"He was London mayor for a long time, and [London] is socially liberal and anti-Brexit. And he took a different tone as mayor to some of his stances while as a Conservative backbencher in Theresa May's government and now PM."

In the immediate future, Johnson is expected to assemble his MPs and to have a modest cabinet shuffle as early as Monday. Brexit legislation is expected to go for a vote before the end of January.

While most of London remained a Labour stronghold, Johnson's win — and the promise of movement on Brexit — was taken as positive in the financial district, with the pound trading higher.

There was no such rejoicing, though, from Labour backers and anti-Brexit campaigners. The Labour supporting Daily Mirror put a big photo of Johnson on the front page with the caption: "The Nightmare before Christmas."

For conservatives, however, a big majority and clear path ahead for Brexit is nothing short of a dream that only a few months ago seemed unattainable.