Polls opened at 7 a.m. local time (11:30 a.m. IST), with many building up large queues, and will close at 10 p.m.

Britain on Thursday went to the polls, the turnout of which, particularly by youth, could play a decisive role in determining the outcome. While polls still suggest a Conservative victory, their lead has narrowed sharply in recent weeks, putting at stake the validation of the government’s Brexit strategy that Prime Minister Theresa May had hoped to secure at the ballot box by further increasing her government’s majority.

Polls opened at 7 a.m. local time (11:30 a.m. IST), with many building up large queues, and will close at 10 p.m. The first exit polls will come out by that time, potentially giving the clearest indication of where the results will be headed.

The first set of constituencies will declare the results around midnight local time, with the rest of the country following in the early morning. People numbering 46.9 million are registered to vote across 650 constituencies.

“If I lose just six seats in this election, the government will lose its majority and Jeremy Corbyn will be sitting down with the Prime Ministers, Presidents and Chancellors of Europe in just a few days time,” Ms. May said in a statement published on Thursday morning. “I need your support to strengthen my hand as I negotiate for Britain in Europe,” she added.

While calling the election, Ms. May had hoped that her party would be able to increase its 17-seat majority by both gaining seats from the UK Independence Party (UKIP) as well as benefit from divisions within the Labour Party that had appeared to put many off the party. While the UKIP had done well in many Conservative strongholds in 2015, recent local elections had shown support for the party had collapsed as the Conservatives became the party of Brexit voters, with its focus on leaving the single market and customs union, and its tough immigration proposals.

However, what it failed to count on was the strong campaign run by Labour leader Jeremy Corbyn. His campaign, targeted at the “Many Not the Few”, has inspired those fed up with years of austerity under both Labour and Conservative governments, while simultaneously bringing into the fold many within the party who were sceptical about him at the start.

The Conservatives have suffered a number of blows — with the terrorist attacks in London and Manchester raising questions about their track record on security and foreign policy, and a proposal on raising the costs of social care for the elderly potentially alienating those within one of its core constituencies.

“We cannot continue with these levels of inequality and injustice in our society. Labour will build a Britain that works for the many,” said Mr. Corbyn at a rally in London on Wednesday evening.

Still, polls give the Conservatives a comfortable lead — a Comres poll for The Independent late on Wednesday put the party at 10 points over Labour. The same poll puts the personal ratings of Ms. May at 48% and that of Mr. Corbyn at 39%.

While Mr. Corbyn’s personal ratings have risen in recent weeks, Ms. May’s have fallen, putting into question the party’s strategy of focusing the campaign around her and her track record — the campaign often emphasized “Theresa May and her team” as well as its strength and stability.

However, with polls failing to have predicted the outcome of the 2015 general election and the results of last year’s Brexit referendum, uncertainty remains, with voter turnout potentially playing a significant role.

“It could be very significant. The turnout among voters could well determine whether we have a clear Tory or a close Tory win — the group for which that is particularly uncertain is younger voters who are in general much more pro Labour,” says polling expert Professor John Curtice of Strathclyde University.

The turnout in 2015 was 66.4% and it is expected to be higher this time, amid high levels of support for Labour and Mr. Corbyn personally.