HARI SREENIVASAN: Should they stay or should they go? That's the question facing British voters today as they decide their place in Europe.

Special correspondent Malcolm Brabant has the story from London.

MALCOLM BRABANT: The signs went up and doors to polling stations across Britain opened for an historic day of voting. It's been a bitter campaign to decide whether Britain remains within or exits the 28-member European Union.

Given the momentous nature of the vote, Britons were on edge.

CLAYTON THOMAS, Bar Manager: I don't really know what to expect. And I think if a result comes in kind of early in the morning, everyone might be asleep still, and might wake up to a kind of different future or might wake up to just another day.

MALCOLM BRABANT: The most recent polls show the outcome is too close to call, but bookies are putting the odds on a remain outcome.

The referendum opened a chasm across Britain, stirring nationalist sentiments along the way.

MAN: Tell them to stop intimidation.

MALCOLM BRABANT: And the murder last week of pro-Europe British lawmaker Jo Cox could also influence the outcome.

Here at a market in Ipswich, the divide is clear.

Produce vendor Ian Buxton voted to leave, in the hope of reducing immigration.

IAN BUXTON, Market Vendor: You see all the migrants. What they say, there's thousands of people waiting to come in. I think we will be strong enough on our own.

MALCOLM BRABANT: At a nearby stall, his former schoolmate Steve Singh warned that break would the economy.

STEVE SINGH, Market Vendor: Business-wise, it's easier then to obviously interchange with free Europe and on shipping, so, you know, my vote is to stay in.

MALCOLM BRABANT: Party leaders went to the polls to cast their votes, but refrained from campaigning outright.

And another major factor that's perhaps going to play into this referendum result has been the weather. More than a month's worth of rain has been dumped on London and the Southeast over the past day causing absolute chaos.

Ben Page is the chief executive office of Ipsos MORI, a major polling firm.

BEN PAGE, Chief Executive, Ipsos MORI: It's difficult to see a very, absolutely certain pattern, but it is true that Brexit voters are much more determined than remain voters.

MALCOLM BRABANT: The British pound surged today to its highest level this year because of market speculation that the country will ultimately vote to stay.

The polls closed just over an hour-and-a-half ago. Voting — counting is under way. We're in for a very long night. The final results should be in around about breakfast time tomorrow — Hari.

HARI SREENIVASAN: Malcolm, so now that the polls have closed, what are you hearing? What's the latest?

MALCOLM BRABANT: Well, normally, in these sort of events, you have exit polls, but the broadcasters this time decided that they wouldn't have one, because there was no real model for them.

But we have heard that the United Kingdom Independence Party has had its own poll of about 10,000 people. And shortly around the time the polls closed, their leader, Nigel Farage, said he thought that the remain people had edged it, which seems to be very much like a concession.

He says, though, that the U.K. was a force to be reckoned with and the this independence move wouldn't be going away. Then, to actually consolidate what seems to be this concession, there was also a poll that had been carried out during the course of the day by an Internet polling company called YouGov, and they have been looking at around about 5,000 voters, tracking them during the course of this referendum.

And according to their on-the-day polling, their outcome is that it's 52 percent for remain and 48 percent for those people who want to leave. So, the indications are pretty clear.

Of course, you know, there are maybe sort of as many as 30 million or 35 million votes to be counted during the course of the night, and that could change. But these are pretty good indications. And so, certainly, in the remain camp at the moment, people are looking pretty confident.

HARI SREENIVASAN: How — when you talked to the people in the last couple days as you were reporting this story out, the undecided, are they aware of the consequences? They were undecided voters even up to the polls today.

MALCOLM BRABANT: Yes, I think the undecided voters really have been absolutely critical in this.

And up until today, the opinion polls, which can't necessarily be trusted, are saying that it might be — might have been as many as about 11 percent of the electorate who were undecided.

And last night, there was a very interesting debate on one of the British TV channels which had 100 people who were undecided, and it tracked their emotions during the course of the debate as various issues came up. And at the end of that debate, what happened was that most of those people who were undecided did vote to remain.

And what probably happened is that I think there are lots of people in Britain who have just been really bewildered by the arguments. They're not able to make up their minds at all. And it's a pretty momentous decision to have to go into that voting booth and to make up your mind, because the decision that was — is made today is completely irrevocable.

To leave the European Union, there will be no sort of coming back. And, for many people, this has been a campaign of loathing and fear, loathing on the part of many of the really vehement Brexiters, who hate many of the things that the European Union stands for, especially the unelected and unaccountable representatives, who they believe are dictating to Britain and taking away its sovereignty.

And the fear element has been amongst those people who are worried in particular about the economy. And it is perhaps the economy which has actually driven the — those people in the remain camp perhaps, because the easiest thing to do is to vote for the status quo.

People have been very worried about losing their jobs. They have been worried by predictions by fairly major individuals in industry, people like Sir Richard Branson, who say it would be a complete mistake to come out of the European Union.

So, not knowing what's going to be on the other side of this, that's why perhaps those people who have been undecided have gone into the voting booth and they have decided to opt for the status quo.

HARI SREENIVASAN: All right, special correspondent Malcolm Brabant joining us from London, thanks so much.