Jonathan Eyal Mr David Cameron, Britain's embattled Prime Minister, will spend most of the coming week trying to persuade European leaders that they should wait until his successor is elected at some point in late September before launching into negotiations for Britain's exit from the European Union.

He will have to fight hard, given calls by EU leaders to speed up the divorce proceedings.

Even if he gains that respite from Europe, Mr Cameron faces the equally urgent task of keeping his own country together. For the nationalist government in Scotland is already using Britain's decision to leave the EU as a justification for Scotland to seek independence.

And if Mr Cameron doesn't move fast to address this and other separatist domestic pressures, he may well go down in history as the man who tore up not one, but two unions: the European Union and the United Kingdom.

Last week's referendum in which Britons narrowly decided - by 51.9 per cent to 48.1 per cent - to withdraw from the EU has exposed serious divides between the UK's four component nations: England and Wales voted for Brexit, while Scotland and Northern Ireland were firmly in the camp of those arguing for remaining in the EU.

The gap between Britain's nations is big: In the case of Scotland, the pro-EU option was supported by two-thirds of the electorate. Yet all that counted for little, since the English outnumber the Scots by a factor of 10-to-one, so England's choice to leave Europe ultimately prevailed.

Ms Nicola Sturgeon, who heads Scotland's autonomous government, claims that the Scots' desire to stay in the EU is due to the country's "modern, outward-looking and inclusive"character.

That's a bit of a flattering exaggeration, for although the Scots have welcomed many migrants, their recent history is also overshadowed by tensions between Protestants and Catholics, who still run separate schools and football clubs in cities such as Glasgow.

Nor are the Scots all that enthusiastic about Europe as their nationalist leaders claim them to be: the key reason why the Scots rejected the option of independence offered to them in a referendum in 2014 was because they did not wish to use the euro currency. Deep down, the Scots support Europe because the EU provides a counter-balance to the otherwise overwhelming influence of England, and not because the EU idea is so lovable.

Still, it's obvious that Ms Sturgeon speaks for many when she claims that it would be "democratically unacceptable" for Scotland to be taken out of the EU against its will. Nor is there any doubt that her demand for Scotland to be given a second chance to vote on its independence option once Britain leaves the EU is enjoying domestic support.

And yesterday, Ms Sturgeon, speaking after an an emergency meeting of her Cabinet, said Scotland wanted immediate talks with the EU on protecting its place in the bloc. She said steps would now be taken to ensure the necessary legislation for an independence referendum was in place, further adding pressure on Mr Cameron.

For the moment, Mr Cameron is sticking to the official position that the question of Scottish independence is already settled, and that the matter won't be revisited. But officials in London know this is not a position that can be maintained for long in the face of determined Scottish opposition, which is only likely to increase as the separation negotiations with the EU begin.

An even thornier problem confronts the British government in Northern Ireland. That province also voted decisively for Britain to remain in the EU, and its wish is also likely to be overruled.

The snag is that Northern Ireland is the only part of Britain to have a land border, and that is with Ireland, which will remain a member of the EU.

Britain's departure from the EU will, therefore, mean the imposition of border controls with Ireland, for the first time in centuries, since the two countries did not have border controls before they became members of the EU, and they joined the bloc at the same time.

The prospect of border controls infuriates Irish Catholics in Northern Ireland because it is a painful reminder of their separation from the Irish Republic.

Mr Martin McGuinness, one of the top leaders in Sinn Fein, the ultra-nationalist movement in Irish Catholic politics, has already called for a referendum to unite Northern Ireland with the Irish Republic. "The people of the north of Ireland have made it clear at the polls that they wish to remain in the EU," Mr McGuinness said.

Ms Arlene Foster, the province's First Minister, who belongs to the majority Protestants, has rejected Mr McGuinness' proposal as "predictable as flowers in May".

"I think we are now entering a new era of an even stronger United Kingdom," she said, expressing support for the British government's separation negotiations with the EU.

Still, both Ms Foster and the authorities in London know that the introduction of border controls with Ireland is precisely the sort of emotional subject that can destroy the fragile truce that ended decades of violence between Catholics and Protestants.

Mr Cameron hopes to address many of these problems by offering to include Scottish and Northern Irish representatives in the British team of negotiators with the EU. But even if that were to happen, there are other untidy leftovers from the age of the British Empire which also need addressing.

Gibraltar, a sliver of British territory on the southern tip of Spain, also voted to stay in the EU since its economy depends on trade with Spain. Gibraltarians will now be faced with the unappealing prospect of having to put up with border controls, and Spain is unlikely to be very friendly, since it has a claim to the territory.

Mr Jose Manuel Garcia-Margallo, the acting Spanish Foreign Minister, has already called on Britain to share its sovereignty over Gibraltar with Spain; the idea is that Gibraltar could become a bridge between the two nations. The British government did not even bother to respond to this offer, but the problem of Gibraltar needs to be addressed, and Spain's cooperation will be crucial.

With goodwill, plenty of solutions to these problems exist, and officials in London are already scrambling to formulate them to the prime minister who will replace Mr Cameron.

Still, Britain's exit from the EU remains a journey into the unknown. And one in which the UK's own survival can no longer be taken for granted.