Oliver Wright: A future without Scotland could be distinctly uncomfortable

The risk to England of the new diplomatic cold war between north and south is considerable

The year is 2030. Sixty-four-year-old David Cameron has won his fifth election – though he is now Prime Minister only of England, Wales and Northern Ireland.

Labour under Chuka Umunna has been pushed into third place behind the newly formed English National Party, which has become His Majesty King Henry's official opposition.

Despite going through three leaders in 10 years, Labour has been unable to make up for the seats the party lost in 2020 when its 40 Scottish MPs were ejected from the House of Commons.

Relations with the Republic of Scotland will continue to provide the key challenge for Mr Cameron.

After England's withdrawal from the EU, President Alex Salmond, 76, brings in tough new border controls between the two countries – dubbed "Hadrian's security fence". Mr Cameron withdraws benefits from Scots living in England and requires people with Scottish passports – along with other foreign EU nationals – to register at their local police station.

The blue St Andrew's Saltire was long ago removed from the Union flag, and the risk to England of the new diplomatic cold war between north and south is considerable.

President Salmond is under pressure to cut off supplies of renewable Scottish electricity to England. Energy prices have already risen 400 per cent in the past few years in the wake of spiralling oil prices and the 2028 shale gas disaster which wiped out large parts of Blackpool.

The pound is now trading at just 50c to the new G-euro and some in the Conservative Party consider entering an economic pact with the United States which could see Britain eventually adopting the dollar as its currency.

Mr Cameron says Britain will not be held to ransom by Scots. He refuses to rule out using military force to ensure electricity supplies are not disrupted – despite a pledge by France to protect Scottish independence as part of its commitment under the European Defence Treaty. Mr Cameron points out that historically Britain, Scotland and France being at war is not unusual, and that the British armed forces – now run by G4S and Serco – can prevail against the "auld" enemy.