EU referendum: What will happen if Britain decides to leave the European Union

The polls were wrong again – though not by very much.

They had forecast a narrow victory for Remain, but had also picked up that outers were generally more committed than inners to taking the trouble to go out and vote.

Perhaps it was the weather, or Boris Johnson’s bravura, or the way the immigration crisis was bringing the EU almost to the point of disintegration – whatever the reason, Leave had won by a whisker.

David Cameron rarely looked as tired as when he emerged from Downing Street to address the television cameras on the morning of Friday 24 June. The pundits agreed that he was now so damaged he would have to resign immediately.

Opposition politicians had taken to the airwaves calling for his head.

It was rumoured that Samantha Cameron would be only too happy to see her husband spending more time with his family.

But overnight, Cameron had come under intense pressure from fellow Conservatives to delay his departure.

When the markets opened in Asia, there had begun the worst run on sterling and the worst fall in the stock-market value of British firms that anyone could remember.

It was feared that this downward spiral would only accelerate if the Prime Minister resigned. Several leading Tories who had backed Remain, including Lord Howard, were publicly exhorting him not to go.

As for his own supporters, they feared that if there were a party leadership contest in the afterglow of the referendum result, Johnson would be unstoppable. They were pleading with Cameron to give Johnson time and opportunity to self-destruct.

Adding to the uncertainty was the difference in results in the component parts of the United Kingdom.

In Scotland, as expected, a decisive majority had voted to remain. Nicola Sturgeon had already been on air to say that so far as the Scottish government was concerned, their country had made a clear and unequivocal decision to remain in the EU, and the Westminster government – the “English government”, in Sturgeon’s phrase – had no authority to negotiate a Scottish exit.

The break-up of the United Kingdom was closer to reality than it had ever been.

In Wales, too, a majority had voted to Remain, and Plaid Cymru – one of the beneficiaries of the fall in the Labour vote in the previous month’s election – was hinting that if Scotland had a future in the EU without England, perhaps Wales did too. It was said the Queen was none too enamoured with the prospect of being Queen of the United Kingdom of England and Northern Ireland.

The other political problem which had come into sharp focus overnight was that the Leave campaign had never been clear or united about what kind of future they envisaged, outside the EU.

Nigel Farage was clear enough – out meant out. Parliament’s first job now was to pass legislation to end the right of east Europeans to enter the country seeking work, and, as he put it: “Get back control of our borders and make damn sure the floodgates of mass immigration are kept tightly closed.”

The task of encouraging those who had already immigrated to go back to their countries of origin would come next. But the public knew Farage was an outsider who did not speak for the mainstream Leave campaign.

He had an unexpected ally in Jeremy Corbyn, whose heart had never seemed to be in the Remain camp. The Labour leader too declared the voters’ verdict was final, but his position was undermined when six members of his shadow cabinet publicly contradicted him.

There were also early voices on the continent – albeit minority voices – suggesting that the EU should say goodbye and good riddance to the irksome English. A leading French politician was quick to announce that the arrangement which allowed British customs officers to operate in Calais should be the first casualty of Brexit.

French public opinion seemed to warm quickly to the idea that the entire Calais jungle could be moved, tents and all, across the Channel.

When Johnson was surrounded by cameras as he left his London home early in the morning, he ran his hand through his hair in apparent amazement at his victory, and said “gosh” and “golly”, and seemed astounded when asked by a reporter whether Cameron should resign – as if such an idea had never been heard of before.

“What I would do, if I were in David’s position,” he said, “not that I would ever expect to be, you all understand, but my reaction would be go to Brussels and say ‘Look, guys, this is how bad it has got. The British people think you are so damned useless that they would rather leave the EU than put up with you any longer – what are you going to do about it?”

Was he calling for renegotiation and a second referendum? He seemed not to hear this question as he clambered onto his bicycle and set off on his unsteady way.

Cameron had even less to say as he faced the cameras later in the morning. He announced that in the “unprecedented” circumstances, the Cabinet would seek an emergency meeting of Europe’s Council of Ministers, and took no questions.

As the weeks went by, a vast amount was written and said about Article 50 of the Lisbon Treaty – until almost every adult in the land knew that there was a Lisbon Treaty with an article 50 in it, even if they were unaware of any other treaties binding the UK to Europe, or of the content of articles one to 49, or whether there were any more beyond number 50.

By the end of the summer, there were people in every corner of the land who could state that Article 50 said, among other things, that “a member state which decides to withdraw shall notify the European Council of its intention” – but for as long as Cameron was in Downing Street, his government did no such thing.

Instead, the Prime Minister spent his last weeks in office in an endless round of exhausting talks from which it became firmly established that, while everyone involved sincerely wanted the UK’s membership to continue, no one could think of a mutually satisfactory arrangement that would enable the British Government to hold another referendum.

In October, when Cameron addressed the Conservative conference, everyone knew that it would be his last leader’s speech. That was perhaps just as well, because the hall was full of representatives who believed that he had let them down and was leaving behind a ghastly mess.

Over the summer, Johnson had disappointed those who wished he would fall flat on his face. He had settled in as a middle-ranking Cabinet minister without any career-destroying blunders. He was loyal enough to Cameron to avoid an appearance of disunity, while being disloyal enough to keep the party faithful on his side.

The rapturous reception he got at the Birmingham conference must have turned George Osborne’s heart to ice.

In the event, the leadership contest was closer than some predicted, but Osborne was too closely linked to the losing side in the referendum, and from the start the contest was Boris’s to lose.

In his first week in office, the new Prime Minister attended yet another emergency session of the EU Council of Ministers, where he was expected to end the long uncertainty by invoking Article 50, but appeared to suffer an acute attack of absent-mindedness.

During the negotiations, he talked volubly about British interests, praised his fellow leaders for their handling of the immigration crisis, and quoted a Latin proverb or two, but when asked as he emerged whether he had invoked Article 50, replied: “Sorry, sorry, dammit, gosh, what lovely weather!”

Johnson had studied the movements in the markets. He had been lobbied by big business. He had taken seriously the French threat to dispatch thousands of refugees to Kent. He had assessed the risk that the United Kingdom might come apart – and he had looked into the negotiations that his predecessor had conducted with Britain’s EU partners, before and since the referendum, and had reached the surprising conclusion that, little did he know it, but Cameron had achieved the best deal that the UK could expect in the circumstances.

When he appeared before a rowdy House of Commons to announce, to jeers from behind him and ironic cheers from across the gangway, that he was setting a date for a second referendum, the polls all forecast a clear and decisive victory for Remain.

But the polls had been wrong before...