The United Kingdom has voted by 51.9 per cent to 48.1 per cent to leave the European Union after 43 years in an historic referendum.
Prime Minister David Cameron on Friday announced his resignation in the wake of defeat in the crucial referendum after Britain voted to leave EU in a deadly blow to the 28-nation bloc that triggered a panic reaction in world markets and raised questions over immigration and other issues in the UK after the divorce.
Brexit won finally by a wafer-thin majority of 51.9 per cent in the referendum held on Thursday that also raised questions over the longevity of the Conservative Prime Minister who aggressively campaigned for Remain.
Shortly after the official announcement, Cameron stepped out of 10 Downing Street to make a brief statement in which he announced his intention to resign, saying a new Prime Minister will take charge in October to launch the process to leave EU.
Watched by his wife Samantha, the 49-year-old British leader, who has just completed a little over a year in his second five-year term, assured the world, more specifically the European nations, that there will be no immediate changes in the way people will travel and services will be sold in Britain.
"The country requires a fresh leadership to take this forward. While it is important that I stay on to steady the ship, it is not right to be the captain. I will do everything I can to do to help," Cameron said as his voice choked with emotion.
Describing the referendum as a "giant democratic exercise", the Premier said the "will of the people must be respected" and their "instruction that must be delivered".
"There can be no doubt about the result...I would like to reassure markets and countries around the world that Britain's economy remains fundamentally strong," he said.
"In my view I think we should have a new prime minister in place by the start of the Conservative conference in October," Cameron said.
The Cabinet will meet on Monday and a timetable for him stepping down will be drawn up.
European Union president Donald Tusk said the bloc was determined to stay unified after Britain voted to leave and warned against "hysterical" reactions.
"Today on behalf of the 27 leaders, I can say that we are determined to keep our unity as 27," Tusk told reporters in Brussels.
EU Parliament President Martin Schulz expressed hopes that Britain's decision to leave the EU would not lead to contagion.
"The chain reaction that is being celebrated everywhere now by euroskeptics won't happen," he said.
The EU was the biggest single market in the world and "Great Britain has just cut its ties with that market," Schulz said. The final national result, overturning over four decades of the UK's membership of EU, was officially declared as 51.9 per cent in favour of Brexit and 48.1 per cent in favour of Remain by the UK Electoral Commission's chief counting officer Jenny Watson from ManchesterTown Hall.
Britain, the second largest economy in Europe after Germany, is the second country after Greenland to quit the bloc.
The referendum turnout was declared as 72.2 per cent with over 30 million people turning out to vote, reflecting the highest turnout in the UK since 1992.
A total of 17,410,742 voters emerged as Brexiters compared to the 16,141,241 that sided with Remain, leading to a victory for Brexit by 1,269,501 votes.
Lauding the referendum exercise, Cameron said, "Over 33 million people from England, Scotland, Wales, Northern Ireland and Gibraltar have all had their say. We should be proud of the fact that, in these islands, we trust the people with these big decisions."
"We not only have a parliamentary democracy, but on questions about the arrangements for how we're governed, there are times when it is right to ask the people themselves, and that is what we have done. The British people have voted to leave the European Union, and their will must be respected," he said.
While thanking the Remain campaigners, Cameron also congratulated those who took part in the Leave campaign, for the "spirited and passionate case" that they made.
"It was not a decision that was taken lightly, not least because so many things were said by so many different organisations about the significance of this decision. So there can be no doubt about the result," he said.
Cameron reassured Britons living in European countries, and European citizens living here, that there will be no immediate changes in their circumstances.
"There will be no initial change in the way our people can travel, in the way our goods can move, or the way our services can be sold. We must now prepare for a negotiation with the European Union. This will need to involve the full engagement of the Scottish, Welsh, and Northern Ireland governments to ensure that the interests of all parts of our United Kingdom are protected and advanced," he said.
London, Scotland and Northern Ireland voted strongly to stay in the EU but Brexit held strong in the north of England, the Midlands region, Wales and most English counties, sending world markets into a shock with the Pound Sterling in free-fall.
Cameron, while announcing that he will step down, also said, "I'm very proud and very honoured to have been Prime Minister of this country for six years. I believe we have made great steps, with more people in work than ever before in our history, with reforms to welfare and education, increasing people's life chances, building a bigger and stronger society, keeping our promises to the poorest people in the world, and enabling those who love each other to get married, whatever their sexuality." Cameron, concluded his statement on an emotional note, saying, "I love this country and I feel honoured to have served it and I will do everything I can in future to help this great country succeed."
Bank of England governor Mark Carney moved soon after to also issue a strong statement to try and calm the turmoil unleashed on the world markets.
"We are well prepared for this. The Treasury and the Bank of England have engaged in extensive contingency planning and the Chancellor and I have been in close contact, including through the night and this morning. The Bank will not hesitate to take additional measures as required as those markets adjust and the UK economy moves forward," he said.
"UK banks have raised over 130 billion pounds of capital, and now have more than 600 billion pounds of high quality liquid assets...This substantial capital and huge liquidity gives banks the flexibility they need to continue to lend to UK businesses and households, even during challenging times," Carney said.
Cameron, who has been Prime Minister of the UK for six years, winning a majority second term for his Conservative party in the 2015 General Election, said the country now requires, "strong, determined and committed leadership" to negotiate the UK's future with Europe and the rest of the world.
His most likely successor is believed to be former London mayor Boris Johnson, who was seen to have spearheaded his own campaign to become Prime Minister when he took charge of the Brexit camp earlier this year.
Other senior Conservatives on the bookmaker's list include UK Chancellor George Osborne and home secretary Theresa May.
However, the general view is that the Conservative party leadership will be taken on by a pro-Brexit minister.
There had been much speculation about how the final outcome would impact Cameron's own political future as Prime Minister.
While he repeatedly stressed that the 2015 general election has given him the mandate to continue irrespective of the result, the bitter campaign had exposed a deep divide within his own Conservative party.
It came down to a very personal vote for or against him for Cameron as, in his own words, he had put in his "head, heart and soul" into campaigning for Britain to remain within the EU.
More than 80 Eurosceptic MPs from his party, including leading Vote Leave campaigner Johnson and UK employment minister Priti Patel, had moved quickly to calm the internal party turmoil by urging Cameron to stay on as Prime Minister in a letter delivered to him soon after the polls closed on last night.
"We who are supporters of Vote Leave and members of the Conservative Party thank you for giving the British people a choice of their destiny on 23 June. We believe that whatever the British people decide you have both a mandate and a duty to continue leading the nation implementing our 2015 manifesto," the letter stated.
But there was a significant number who believed his position had become untenable, having campaigned so strongly against the final outcome of Thursday's referendum and warned of a "less safer" country in the event of a Brexit vote.
Opposition Labour leader Jeremy Corbyn, who called for the UK to remain in the EU but was accused of a lukewarm campaign, said poorer communities were "fed up" with cuts and felt "marginalised by successive governments".
"Clearly there are some very difficult days ahead," he said.
The political discourse swiftly moved to the future and what happens next in the event of a Brexit vote.
In the immediate aftermath, Britain will remain a member of the EU and nothing will change instantly.
The British Prime Minister had pledged to activate Article 50 of the 2009 Lisbon Treaty as soon as possible if the result of the referendum was to leave the EU.
The Article begins negotiations with the EU's 27 member states for the UK's exit.
That process could take two years or longer, with scope to extend the negotiation period if all parties agree, with 2020 as a potential timeline when the next UK General Election is to take place.
The renegotiation will involve a series of agreements with world trade bodies and Britain deciding what kind of an economic and political relationship it would strike with Europe, its biggest trading partner.
Once Article 50 has been triggered, the only way back into the EU is with the agreement of all member states.
The wider consequences also involve a question mark on the future of Scotland, which has voted overwhelmingly in favour of Remain.
Scottish First Minister Nicola Sturgeon has indicated that it would mean a rethink on its relation within the United Kingdom to keep its EU membership.
"Scotland has delivered a strong, unequivocal vote to remain in the EU, and I welcome that endorsement of our European status. And while the overall result remains to be declared, the vote here makes clear that the people of Scotland see their future as part of the European Union," she said.
The Vote Leave camp, which included Indian-origin MPs Priti Patel, Cameron's Indian Diaspora Champion, and Infosys chief Narayana Murthy's son-in-law Rishi Sunak, had said in a campaign note recently that, "Britain's trade policy is controlled by the EU."
Commonwealth countries like India have been in talks with the EU about doing a trade deal since 2007 but to no avail.
Another Indian-origin MP and Cameron's Infrastructure Envoy to India, Alok Sharma, on the Leave side, had argued that EU membership meant a "seat at the table as the EU negotiates some of the biggest trade deals in history -- such as the ongoing discussions with the United States, China and India".
In terms of broad trends, the vote reflected a very divided country.