Iain Macwhirter: Scexit 2028: How Scotland can learn from the Brexit shambles how NOT to leave a Union

Mr Robertson accused London of behaving in a “curmudgeonly and destructive” manner which makes Brexit in 2020 look like a chat between old friends. “This will only make the Scottish people more determined”, he told the Scottish Parliament at Question Time, “to assert their natural right to sovereignty and be free forever from colonial diktat”.

Ms Joanna Cherry, who has been leading what tabloid newspapers call the “Scexit” negotiations, has said London is behaving “like tinpot imperialists”. She insists that a common travel area has existed across the entire United Kingdom since the 1920s, and there is no hard border in Ireland between Britain and the EU. The UK Supreme Court, she said, should rule that the UK government is acting unlawfully.

During the transition period, the court is still technically the highest court for both Scotland and England. It made a historic ruling on the Scottish parliament's right to hold an advisory referendum on independence. But judges insist they cannot interfere with treaty negotiations.

There is no doubt that imposing border checks and tariffs on Scotland would damage the rest of the UK, and few believe that Mr Gove is serious. But the UK lead negotiator, Lord Forsyth, has said that, since Scotland intends to rejoin the European Union and has been offered fast-track entry by Brussels, Britain has to protect its national interest.

“All we are doing”, he has said about the checks, “is preparing the ground for what is inevitable when Scotland hands over its newly-won independence to the bureaucrats of Brussels”. Unless Scotland agrees to regulatory alignment with the UK after rejoining the EU, there must be checks and tariffs. He added that there can be no “read-across” from Northern Ireland to Scotland, since the absence of a hard border with the Republic was a requirement of the Good Friday Agreement of 1998.

There was widespread anger in Scotland when the UK government started imposing unilateral sanitary and phytosanitary checks on food and agricultural produce entering the rUK. These have been described by the Labour leader, Sir Keir Starmer, as being “as punitive as they are pointless”. Labour have called for both sides to conduct negotiations in a spirit of mutual respect.

There is precious little of that around as the social media war rages like an Australian bush fire. Twitter has rejected calls from the Scottish government to block the #jockoff hashtag campaign which has been trending all year. Mr Robertson says it is fomenting racial abuse illegal under the Scottish Hate Crime Act.

The UK press has been almost universally hostile to Scotland's negotiating position and the tabloids have been flirting with what Joanna Cherry has called “blatant anti-Scottish racism”. She has been portrayed as “Jo Cherry-pick” by cartoonists in unflattering images that the Scottish Government claim are misogynistic. There were scuffles as Nigel Farage addressed the Sun newspaper's latest “Scexit Now” rally at Berwick.

Some important matters have been resolved in the past hectic weeks. The UK government has withdrawn its threat to erect border posts on the M6. Agreement has been reached in principle on the operation of the common energy grid after independence. English universities will still recognise Scottish highers exams and academic qualifications. The BBC has promised not to axe BBC Scotland. Even the contentious issue of fishing seems to have been resolved.

However, the Bank of England is refusing to say whether it will recognise the Scottish pound after independence day. The Scottish Government has proposed to use sterling as a temporary measure until it can establish an independent currency of its own, as laid out in the Sustainable Growth Commission Report. “Try and stop us” said Mr Robertson yesterday insisting that the bank is powerless to prevent Scotland tying its pound to a reserve currency.

The UK government surprised many last year when it called for Scotland to remain in a formal currency union with the rest of the UK. This indeed used to be SNP policy. But independence supporters said that would mean Scotland being tied to UK interest rates and unable to manage its own economy. It would also be a potential barrier to Scottish entry to the European Union since the Maastricht Treaty requires accession states to have their own currency and central bank.

Behind it all lies the vexed issue of Trident. The UK government is demanding that the British nuclear deterrent remain in the Clyde for at least 20 years after independence. This is anathema to long-standing SNP activists, though the First Minister is thought to believe a compromise is possible when an independent Scotland rejoins Nato, a nuclear alliance. London has made clear that it will look again at the border issue if Scotland agrees to a common defence pact that protects the security of the entire United Kingdom.

The leader of what is being called “Continuity SNP”, Alex Salmond, has told supporters at a mass rally in Glasgow that to keep Trident in the Clyde would be an “abomination piled upon humiliation” He accused the Scottish government of being “recklessly incompetent” during the negotiations, “when it hasn't actually been holding up its hands in surrender”.

The reality is that both sides have everything to gain from an amicable separation and an awful lot to lose. Even after it rejoins the EU, Scotland's main trading partner will be England and the rest of the UK. The fragile rUK economy does not need another economic shock so soon after the end of the Brexit recession.

Perhaps both sides should have learned from those disastrous Brexit negotiations that it is unwise to allow a transition phase to continue for years. The break should be short, sharp and decisive, and based on a joint declaration affirming the principle of self-determination.

Negotiations have been made harder than necessary by the failure of both sides to recognise reality. London never fully accepted that Scotland was becoming a sovereign nation. The government of Scotland should have accepted that since Scotland will remain part of the broader “New UK of the Isles”, this would entail compromise.

Historians argued that the Westminster government should have passed a short Statute of Westminster, as it did in 1931 for Canada and other dominions. This would have simply stated that Westminster would no longer legislate for Holyrood. Scotland could have remained part of a new UK of self-governing countries under the UK crown. It could have been the start of a new partnership based on mutual respect and independence. Unfortunately, politics got in the way and we are where we are. What happens now remains to be seen, but as yet there is no sign that Scots regret having voted Yes in Indyref2.