A marriage that has lasted for almost 300 years must have something going for it. The evidence, however, is that there is increasing momentum for a trial separation, even divorce, in England as well as Scotland. Yesterday was the anniversary of the original Scottish Parliament voting itself out of existence. The response of Scottish politicians who support the Union was strikingly defensive in character. Their equivalents in England, personified by Tony Blair at his press conference, emphasised the dire economic risks that those who favour Scottish independence were entertaining.

In a sense, it was ever thus. Strategic calculation and economic opportunism have long been central to the story of this relationship. England’s parliamentarians favoured the Union of the two nations to ensure that Scotland could not make common cause with France and would endorse the same Hanoverian succession after the death of Queen Anne. Their counterparts in Scotland wanted to be part of what would then be the largest free-trade area in Europe and have the right to sell on the same terms to England’s colonies in North America and the West Indies. It was an arranged marriage rather than one of true love.

That being so, why does it continue? There is not much chance of Scotland being the back door for a French invasion; the Hanoverians morphed into the House of Windsor some time ago; both England and Scotland are part of (and would continue to be members of) a larger free-trade zone called the European Union; and there are very few “English” colonies to be found anywhere.

If the politics of the financial sliderule were all that held England and Scotland together, then the case for the dignified parting that took place between the Czech Republic and Slovakia in the 1990s would be irresistible. Scotland might well be worse off in the short term, but the claim that the country is “too small” to survive on its own is incredible when a map of Europe today is more fragmented than at any moment since the Holy Roman Empire. England might be slightly richer if it ceased to “subsidise” its neighbour but the difference it would make to its gross domestic product would, in truth, be marginal. Monetary advantage alone cannot be the reason either why Scotland would want to remain attached to England or why anyone in England should rationally wish to bid her old partner a prompt farewell.

It is the Union not of Parliament but peoples that has ensured that the United Kingdom has endured. It is that link which is worthy of celebration this year. It is symbolised by the fact that so many people who were born in England or Scotland now live in the other country or are married to those from across the Border and that millions of families in the north or south can trace their ancestry or surnames to the opposite side of the imaginary fence. These are bonds strong enough to allow for a revival of pride in what it is to be a Scot, or to be English for that matter. What has to be averted is a destructive auction of raw nationalism in which England and Scotland come to define themselves by their differences.

This is eminently avoidable. Whatever the undoubted difficulties that surround the “English Question”, the idea that it can only be solved by dissolving the Union is unappealing. So is the notion that the English and the Scots should treat each other as if they were foreigners. Expectations of marriage may not be quite the same in 2007 as they were three centuries earlier. With a little careful marriage counselling, this relationship should endure far into the future.