What will happen next is difficult to predict. A long, hard road of negotiations between the UK and EU beckons although it is unclear when this process - likely to take years - will begin.
Britain has voted to leave the European Union. The consequences are colossal and numerous, but what happens in the immediate aftermath of the vote?
The first thing to say is that Britain does not leave the bloc immediately. This is just the start of a process that is likely to take years, according to constitutional experts. Even before any talks get under way, there are some immediate political and economic consequences to deal with.
There could be an emergency EU meeting, where leaders could begin to deal with Britain’s historic decision, which has huge knock-on consequences for the rest of the bloc. A major European Council meeting of leaders was due to take place at the end of the month but the world has now changed that it could be brought forward.
The major step will be when Britain formally begins triggers negotiations about leaving the EU. This is known as triggering Article 50 and the government will have two years to thrash out an exit deal. If no deal is reached, Britain will leave the bloc with no deal and it would with have a trading arrangement with the EU under international rules set out by the World Trade Organisation (WTO). Talks can be extended beyond two years, but any EU state can veto an extension.
One of the big questions is when Article 50 will be triggered. Those in charge of the Brexit campaign have said that it need should not be triggered straight away in order for informal talks to take place with EU leaders first. Britain’s trading relationship will be crucial.
There is no one model for what Brexit looks like and the process for deciding it is hugely messy. Pro-Remain MPs could use votes in parliament in an attempt to keep Britain in the EU’s single market. That would avoid trade tariffs, but the UK would almost certainly have to accept the EU’s free movement rules, which drove many voters to back Brexit. However, whatever MPs want, it also depends on what kind of deal EU leaders are willing to give Britain.
The prime minister, whoever that may be after Mr Cameron’s decision to resign today, will have to appoint a team to oversee Britain’s exit talks. It is likely to have to be a senior supporter of Brexit – perhaps someone like Michael Gove. There may also need to be a swift government reshuffle as Brexiteers are put in senior posts. There are serious questions over the future of George Osborne, whose deficit-reduction plan will be in tatters as a result of the economic impact of Brexit.
George Osborne angered MPs during the EU referendum campaign by saying he would have to use an emergency Brexit budget to plug a £30 billion black hole in the country’s finances. Was it a campaigning ploy or will an emergency budget in some guise take place?
With Scotland voting in favour of the Remain campaign, there have been calls for a second referendum on Scottish independence and Brexit has been cited as an explicit circumstance in which the SNP may demand one.
There have been suggestions that there will now have to be a hard border between southern and Northern Ireland as a result of the Brexit vote. Emergency meetings are already planned in the Irish government. Sinn Féin has said there is a “democratic imperative” for a poll over the border staying in place after Northern Ireland voted to remain.
Michael Savage, Chief Political Correspondent – The Times