This could be the year that Great Britain comes to an end. The prospect is historically momentous. Yet it is one that appears to evoke nothing more than a yawn from most English people. The reason, I assume, is that to them it does not much matter. They have moved on from such things.

We tend to forget that the confederacy to which most of us owe loyalty – the United Kingdom – was invented only in 1801 and lasted until 1922. The so-called UK survives only by the thread of Northern Ireland. As for Great Britain, it was a joint monarchy declared by James I in 1604, generously embracing Ireland and France. It became a single state under one parliament only in 1707 (without Ireland, then still a colony). If the Scots do vote for independence in this year's referendum there will doubtless be some new treaty to replace the act of union, but Great Britain will be no more.

I doubt if church bells will toll or many English heads hang in shame. Britain will probably live on as our old statutory friend, England and Wales. There is little England can do about it either way. Lecturing, scaring and threatening the Scots, as London politicians keep doing, is like a parent warning a teenager against going to the pub. The English are supposed to believe in self-determination. They have gone to war for that cause in the Falklands, Kurdistan and Kosovo, though admittedly they ditched the "overseas" British of Hong Kong and Diego Garcia when it suited them.

As for self-determination in Northern Ireland, it has meant decades of bloodshed and communal partition that is far from over. This survival of a token "united kingdom" has always so embarrassed the Westminster political parties that they never dared set up shop there. An American diplomat has even had to be brought in to settle – or fail to settle – the province's archaic feuds over flags and marches.

If Great Britain is no more I shall be sorry. But the sorrow will not be for the loss of Scotland, any more than I might have been "sorry" for the loss of Ireland. I regard these places as proper countries and if they seek to "lose England" that is entirely their business. The UK claims the right to withdraw from its treaty with the European Union. Edinburgh can likewise withdraw from its treaty with London. But I would be ashamed of an English political culture whose insensitivity to the aspiration of what it calls its "Celtic fringe" ended three centuries of creative partnership.

Margaret Thatcher started the rot by imposing her poll tax on the Scots as a "pilot". Not since George III and the American colonies was an impost so stupidly counter-productive to empire. Coupled with the deindustrialisation of Glasgow, the poll tax wiped out the Tories north of the border. Thatcher's successor, John Major, failed to get the message and fought against devolution. Tony Blair did get it, and realised that continued Anglo centralism would threaten the union. He revived the Edinburgh parliament but foolishly failed to delegate to it fiscal autonomy and thus budgetary accountability. He bought Scottish loyalty with a subsidy that gave them £1,000 a head more than the English, and allowed the Scots to think welfare grew on trees.

The arguments advanced at Westminster against independence are as if British "localism" were still a matter of country dancing, local radio and separate teams for the World Cup. George Osborne for the Tories and Alistair Darling for Labour treat the Scots as not grown-up enough to judge their own interests, and should be told they may lose their pocket money. To them, devolution is a privilege to be earned, not a right to self-government to be honoured. Needless to say, when Brussels treats London in this way, these same politicians regard it as an impertinence.

Across Europe – in Spain, Belgium, Italy and now Ukraine – central governments are struggling with a new nationalism, as provinces assert political identity against the forces of global homogeneity. In former Czechoslovakia and Yugoslavia that struggle failed. In Spain it may yet fail. The reason, almost invariably, is central contempt for subordinate autonomy. This is why Britain lost America, and Ireland under the Liberal-Conservative coalition in 1922.

If I was a Tory strategist, I would make light of a Scottish yes vote, indeed I might encourage it. I would portray the nationalist leader, Alex Salmond, as a one-tune populist, drunk on welfare transfers and windfarm subsidies. If Scotland wants to be rid of the London exchequer and to ruin its tourist economy, so be it. If it thinks oil taxes will replace subsidies, fine. If Salmond repatriates Labour's Macmafia of 40 London MPs, good luck to him – and them.

Salmond's November prospectus for a new Scotland was so full of holes that it suggested a decade of false hopes, economic woes, political shambles and austerity, before reaping the undoubted gains of small-countries-are-beautiful. There is no reason why one day Scotland should not be the new Denmark. But it will take time.

All this would be entirely to the benefit of England's Tories. It makes their passion for union puzzling and renders senseless treating the Scottish referendum as almost a vote of confidence in David Cameron. Even if no more than 40% of Scots vote for independence, this would still do serious damage to the union. Without more ado, the Tories would be wise now to propose de facto autonomy under the crown – "devo max" – in the manner of the Basques and the Catalans.

The truth is that for many English politicians the argument has little to do with Scotland as such. It is a genetic hangover from the concept of "manifest destiny" for great power status that still attaches to the London establishment. However much England's domestic "empire" dwindles, its leaders learn nothing and cling like jealous guardians desperately to what is left. As Thomas Jefferson said of them during the American revolution: "I never yet found any general rule for foretelling what they will do, but that of examining what they ought not to do."

One thing is for sure, if David Cameron and his coalition succeed in losing Scotland in the coming year, Wales will be next. England will have contrived in a century to lose not one empire, but two.