Boris Johnson was campaigning into the final hours of election day as parties braced for the 10pm exit poll.
The Prime Minister tweeted photos of himself in his constituency of Uxbridge and South Ruislip with the familiar rallying cry of “vote Conservative #GetBrexitDone”.
Mr Johnson started his day by voting at the Central Methodist Hall in Westminster at around 8.15am, bringing dog Dilyn along with him.
Labour Party leader Jeremy Corbyn was greeted by a small number of supporters as he arrived to cast his vote in Islington – and a protester dressed as Sesame Street character Elmo.
As the woman in fancy dress argued with security and police, Mr Corbyn said: “Hello guys, can we stop the arguments please.”
He later posed for photographs with well-wishers outside the polling station.
Mr Johnson’s campaign has maintained a laser focus on delivering Brexit, while Mr Corbyn has tried to highlight his party’s credentials on the health service and other domestic issues.
In Scotland, First Minister Nicola Sturgeon was joined by her partner Peter Murrell, as well as the SNP’s Glasgow East candidate David Linden, in voting at Broomhouse Community Hall in Uddingston, South Lanarkshire.
Lib Dem leader Jo Swinson and her partner Duncan Hames were also out early to vote at a school in Glasgow.
It comes as the polls have narrowed in the final week of what has largely been a tame campaign – with few gaffes and many stage-managed visits.
On Monday Mr Johnson came under fire for his alleged lack of empathy when he pocketed a journalist’s phone when asked to view a photograph of a four-year-old boy who was forced to sleep on a hospital floor.
The following day, however, Labour’s campaign was rocked when a member of the shadow cabinet was revealed to have poured scorn on Mr Corbyn’s election chances in a leaked recording.
A terror attack on London Bridge – which echoed a similar incident in the middle of the 2017 election – briefly disrupted the campaign, but quickly turned political as the Tories and Labour exchanged blows over how to deal with such threats.
The third General Election in less than five years has been largely dominated by the 2016 vote to leave the European Union – with Labour pledging to give voters another say in a second referendum, while the Tories have vowed to take the UK out of the EU next month.
A poll by The Daily Telegraph and Savanta ComRes, published on Wednesday night, placed the Tories five points ahead of Mr Corbyn’s party – indicating the potential for a Conservative majority or a hung parliament.
But a separate poll by Kantar put the Tories on 44%, Labour on 32% and the Liberal Democrats on 13%.
Voter turnout, however, could play a major role in the election outcome with rain, wind and chilly temperatures forecast for much of the country throughout Thursday. But some polling stations reported long queues despite the miserable weather.
In a final plea to voters on the eve of polling day, Mr Johnson warned that the election remained on a “knife edge”, but said it represented a chance to “end the gridlock”.
“Today is our chance to unite as a country and put the uncertainty to bed so people can get on with their lives,” he told supporters in east London.
“Just imagine how wonderful it will be to settle down to a turkey dinner this Christmas with Brexit decided – and how awful it would be if Corbyn and Sturgeon were in Downing Street advancing their plans for two more referendums.
“Let’s stop the chaos and stop the referendums. We can secure a majority Conservative government if we win just nine more seats.”
Mr Corbyn, meanwhile, stressed the “very profound” issues at stake in Thursday’s vote.
“We’re literally at a fork in the road,” he told the party faithful at a rally in north east London.
“So when the election comes tomorrow it is a very clear choice. You go down the road of Boris Johnson, a sweetheart deal with Donald Trump, we break off any serious relationship with Europe.
“Or you go down the Labour way, which is the adult, responsible way, of negotiating a settlement which we will all live by, and I will make sure is carried out in a future relationship with Europe.
“But we also go down the road of investing in our country, investing to end austerity and redistributing wealth and power in our society in a way that’s never been seen before.”
Liberal Democrats leader Jo Swinson said the polls showed it was still “absolutely possible” to deny the Tories an overall majority through tactical voting.
“We know from past elections that, very often, voters who vote tactically come to that conclusion in the final hours before they cast their vote,” she said.
Brexit Party leader Nigel Farage, speaking in Doncaster, said he was hoping for “very, very heavy rain” in the town on Thursday, in the belief that it would depress the votes of the other parties.
“I know that people who are going to vote for us will turn out, because they absolutely believe in our message, they believe in their hearts as well as in their heads,” he said.