As the night wore on, the bottles remained unopened and the party went decidedly flat.

To everyone’s shock and dismay, the Tories not only won the 1992 general election, they actually gained two seats in Scotland.

It was the last time the Tories won a general election – until now. The 1992 result led to a largely spontaneous outpouring of anti- Conservative feeling on the streets of Scotland.

The return of Tory rule, following Margaret Thatcher, two devastating recessions and the poll tax, was a profound shock to social democratic Scotland.

Celebrated trades union leader, the late Bill Speirs, led the formation of the Scottish anti-Conservative front Scotland United along with Labour MPs such as George Galloway and John McAllion as well as prominent cultural Scots like Pat Kane of Hue and Cry and Ricky Ross of Deacon Blue.

Even SNP politicians such as Mike Russell, who had boycotted the cross-party Scottish Constitutional Convention only four years previously, joined Scotland United demonstrations, which culminated in a 25,000-strong rally in Edinburgh at the European summit in December 1992.

Could history repeat itself? In a matter of months, Scotland could, if the opinion polls are accurate, wake up to find itself back under Conservative rule from Westminster for the first time in 13 years, and with an increased number of Scottish Conservative MPs. Will it be 1992 all over again?

Could the shock of Tory rule be the spark that reignites the constitutional debate in Scotland and prepares the ground for another referendum, this time on independence? Will Pat Kane come out of semi-retirement and form Scotland Re-United on a bill with a Deacon Blue tribute band? Probably not.

Things are very different today, and popular music has moved on. We also have a Scottish parliament with wide-ranging powers over domestic affairs, which the Conservatives no longer oppose.

But what we are likely to witness if David Cameron wins in May 2010 is the original “nightmare scenario” envisaged 30 years ago by critics of devolution such as Labour MP Tam Dalyell, author of the West Lothian Question, who argued that devolution was “a motorway to independence with no U-turns and no exits”.

It was precisely this combination of a Nationalist government in Edinburgh and a Conservative one in London which opponents of home rule believed would ultimately tear the union apart.

More recently, the deputy leader of the Liberal Democrats, Vince Cable, has echoed this warning, telling last month’s LibDem conference that he expects “conflict and possible secession” after a Tory victory.

Could David Cameron become the last prime minister of the United Kingdom as we know it? Certainly, a Tory government in Westminster is an important element in Alex Salmond’s game plan for winning independence.

David Cameron is not Margaret Thatcher, and he has effectively apologised for the impact of her economic policies on Scotland. He has promised to rule Scotland “with respect”.

But he is also committed to very deep cuts in public spending. Since a disproportionate number of Scots are employed by the public sector, the proposed 10% cuts in departmental budgets – on top of the SNP government’s own 2% efficiency savings – could lead to tens of thousands of lost Scottish jobs.

The SNP will present this as another London-inspired economic holocaust, equivalent to the Thatcherite industrial recessions of the 1980s. Only this time The Proclaimers will be singing: “Schools no more, nurses no more, care homes no more ...”

The Nationalists hope that a Scottish reaction against the Cameron Tories in Westminster will secure them victory in the 2011 Scottish elections, and make the case for a referendum unanswerable. Has not Lord Forsyth, the former Tory Scottish secretary, himself called for a referendum on independence?

Have the Cameron Conservatives not promised a referendum on the Lisbon Treaty on the EU constitution?

How then, say the SNP, could an incoming Tory government refuse a referendum on independence after two SNP election victories in Scotland? Journalists north and south of the Border are already honing their superlatives in anticipation.

It could be a great story: the final unravelling of the United Kingdom constitution after 300 years, destroyed by a collision between the unstoppable force of English Conservatism and the immovable object of Scottish Nationalism.

It’s a plausible enough scenario, but it is all perhaps just a little too neat.

History doesn’t repeat itself as literally as that. Indeed, the danger for the Nationalists, and for Scottish Labour as they brace themselves for the new Tory age, is that they end up fighting the battles of the past, and fail to appreciate that Scotland has changed in the past 20 years.

For many Scots, Thatcher and her poll tax are now ancient history. Scotland is a different country, and in many ways a small-C conservative one – at least in that it is now predominantly middle-class, home-owning and apparently rather conventional in its attitudes to things like multiculturalism and gay rights.

Curiously, the Scottish Tories have singularly failed to capitalise on this to any significant extent, and have actually been losing ground in recent polls on Scottish voting intentions.

There has been no Cameron bounce – which is why the Scottish Sun did not join its UK parent last week in throwing its support behind the Tories.

Yet the Tories remain the only party in Scotland to have won a majority of votes and a majority of seats in a general election – that was in 1955, when people still talked of Glasgow as the Second City of the British Empire.

Protestant Unionism was a powerful force in postwar Scotland and, even as late as 1979, when Margaret Thatcher was elected, the Conservatives had 22 Scottish MPs and dominated politics in both Glasgow and Labour councils.

It was of course “that bloody woman”, as she was called on the doorsteps in the 1987 general election, and her poll tax, which drove the final nails into the coffin of Scottish Conservatism. The two great industrial recessions in the 1980s, from which communities in west-central Scotland have yet to recover, plus the hugely unpopular community charge, have been seared into Scottish political folk memory. “Tory” became a four-letter word and many dismissed them as “the English party”, for their opposition to devolution.

The Conservatives gained two seats in 1992, against the trend, but were wiped out in the 1997 general election – as the Scotland United generation wreaked its vengeance. There remains only one Tory MP in Scotland, and if it hadn’t been for the Scottish parliament and proportional representation, they might have disappeared altogether.

The Conservatives still live under the shadow of the 1980s, which remains an obstacle to their electoral recovery.

But while middle Scotland remains largely immune to the appeal of Conservatism, that doesn’t mean that Scots are going to take instantly to the streets in outrage at David Cameron entering Number 10. The passion isn’t there any more.

The great achievement of the Scottish parliament over the last decade has been to defuse the Scottish grievance culture. We no longer automatically blame London for everything that goes wrong. The Scotland Reunited scenario also assumes that David Cameron will follow the neo-Thatcherite script, which is not certain by any means. The Tory leader does not want to go down in history as the prime minister who presided over the break-up of Britain.

He will do everything in his power to avoid an early confrontation with the Scottish government, and it is not inconceivable that Cameron might even accept a referendum on independence – although only if he is reasonably confident of winning it.

He has been careful not to rule it out. Tory commentators such as Fraser Nelson of The Spectator say a referendum would be a way of rebutting the claim that the Tories have “no mandate to rule” in Scotland by reaffirming support for the union.

But, with or without a referendum on independence, Cameron’s best bet for saving the union would be to adapt it to changed circumstances. Had there been any sign of an imminent Tory revival in Scotland, he might have been able to tough out the inevitable confrontation with the Nationalists. But the signal failure of the Scottish Conservatives to thrive electorally – their best hope for the general election is five or six seats – rules this out. It would look too much like an “English” party imposing a diktat over Scotland. A better option would be to seek a deal with Alex Salmond – a historic compromise between Nationalism and Unionism.

That may seem outlandish, but, remember, Alex Salmond is in Bute House only because the Scottish Tories were prepared to back him as first minister after the 2007 Holyrood election.

After that, the Tories struck a “devil’s bargain” with the SNP, supporting Salmond in power in exchange for influence. Annabel Goldie, the Scottish Tory leader, claimed a series of policy concessions, including more police on the beat and a cut in business rates.

On the whole it has worked: it gave them something to talk about, and the Scottish Tories no longer face electoral oblivion. A new deal on the UK might similarly give the Conservative government in Westminster a “stake” in Scottish

politics and provide the basis for recovery. All David Cameron needs to do is adopt some of the recommendations of the Calman Commission, which the Scottish Conservatives endorsed, and give the Scottish parliament greater tax-raising powers.

This could kill two birds with one stone: diverting attention from the ongoing spending cuts while scrapping the Barnett Formula, which many English Tory MPs believe gives Scotland an unfair advantage in public spending.

There is nothing that says the union would end just because Scotland raised its own taxes. For their part, the SNP might well be in the mood for a compromise, especially since support for independence shows little sign of increasing following the recession which showed the Scottish economy to be dangerously exposed to banking crises.

The SNP has recently been talking increasingly in terms of a new “social Union”: a new relationship in which Scotland retains the Queen as head of state, shares the network of UK embassies abroad, retains the pound as the Scottish currency, and upholds the values of common UK institutions such as the integrated National Health Service.

It could be argued that the SNP has given up on independence, in the old secessionist sense. Perhaps one day we might even see Alex Salmond and David Cameron meeting at Buckingham Palace to unveil to the Queen their blueprint for a new improved federal United Kingdom.

Could the shock of Tory rule be the spark that reignites the constitutional debate in Scotland and prepares the ground for another referendum, this time on independence?