London: Millions of Britons began voting on Thursday in a bitterly-fought, knife-edge referendum that could tear up the island nation's EU membership and spark the greatest emergency of the bloc's 60-year history.
A record 46.5 million voters have registered to decide on Britain's future in the 28-nation European Union, which was born out of a determination to forge lasting peace in the continent after the carnage of two world wars.
The once-in-a-generation referendum asks: "Should the United Kingdom remain a member of the European Union or leave the European Union?"
Each voter must draw a cross by one of two options:
- "Remain a member of the European Union"
- "Leave the European Union"
As voters in a rain-swept London headed to polling stations, world financial markets were in suspense over the result.
With no exit polls under way, the result is unlikely to begin emerging before about 0300 GMT Friday.
On the eve of the historic referendum, two polls -- both conducted over the Internet -- put the "Leave" camp ahead by one or two percentage points, well within the margin of error.
In one telephone poll, however, "Remain" took a notable lead of 48 percent, ahead of "Leave" on 42 percent with the rest undecided, according a survey by ComRes for the Daily Mail and ITV News.
Read: Britain votes on EU membership after tight and bitter campaign
Financial institutions are reinforcing teams to cope with the prospect of frantic trading through the day and the world's leading central banks say they are ready to react to any eventuality.
'Independence Day'
The often acrimonious, deeply-emotional campaign has exposed a gulf among Britons on membership of Europe.
The Thursday editions of British newspapers captured the drama of voting day. "Independence day" was the headline of the pro-Brexit Sun, while The Times called it a "Day of reckoning".
Leading Brexit backer Boris Johnson, a former London mayor who is widely touted as a future prime minister, insisted the "Leave" campaign was on the brink of victory.
"I do think that we are on the verge, possibly, of an extraordinary event in the history of our country and indeed in the whole of Europe," Johnson said in eastern England in a final scramble for support on Wednesday.
Prime Minister David Cameron, who has staked his political legacy on the referendum, implored people to vote to stay in the bloc at a final rally in Birmingham on the eve of voting.
"Winston Churchill didn't give up on European democracy... and we shouldn't walk away," he said.
"Our economy will suffer if we leave," he warned.
'Out is out'
"If you jump out of the aeroplane, you cannot clamber back through the cockpit hatch. That is why anyone in any doubt should vote remain tomorrow."
EU leaders warned Britons that there would be no turning back from a vote to quit.
"Out is out," European Commission chief Jean-Claude Juncker said in Brussels on Wednesday, dismissing any talk of a post-vote renegotiation of Britain's membership terms.
French President Francois Hollande warned an exit would be "irreversible".
A British withdrawal from the EU would trigger a lengthy exit negotiation, leading to the loss of unfettered access to its partners in the EU's single market and forcing the country to strike its own trade accords across the world.
In Europe, the referendum has raised concerns of a domino effect of exit votes that would imperil the integrity of the bloc, already buffeted by the eurozone and migration crises.
Though many voters fret over the financial consequences of a Brexit, others relish the prospect of taking back power from Brussels and reining in high levels of immigration.
The referendum battle had paused for three days to honour the brutal murder of Jo Cox, a pro-"Remain" British lawmaker and mother of two who was stabbed, shot and left bleeding to death on the pavement a week ahead of the vote.
"Jo's killing was political. It was an act of terror," her husband Brendan Cox told around 5,000 people gathered in London's Trafalgar Square on Wednesday on what would have been her 42nd birthday.
Thomas Mair, 52, has been charged with Cox's murder.
On his first appearance in court on Saturday, he gave his name as "Death to traitors, freedom for Britain".
A psychiatric report was requested.
EU leaders will open a two-day summit in Brussels on Tuesday to deal with the result and decide how to cope with the risk of similar referendums on the continent that could threaten the bloc's integrity.
