If the eurozone states do follow the logic of their botched monetary union, they will next opt for a single treasury and fiscal union to run southern Europe according to German rules. That would leave the ten members of the EU not in the single currency, including the UK and conceivably an independent Scotland, in an interesting position. It would mean a "two-speed Europe" with Scotland trying to ride two horses, simultaneously seeking to separate itself from England but not being inside the much more closely integrated eurozone either. In any event, it is now difficult to imagine the Germans agreeing to such full-scale fiscal integration. More likely is the eventual disintegration of the euro, or its splitting into blocs with the weakest countries falling out entirely.

For a small country such as Scotland, perched on the edge of Europe, such instability would be dangerous. At such a time being in a sound partnership with a bigger neighbour — one with which you share a language, an economy and a history of joint endeavour — could be just the ticket. Luckily for the Scots they have an obvious answer on hand if they want it: maintaining the existing Union with England.

What is left of the Labour party in Scotland has barely even begun to engage with such arguments. The referendum, which I expect Salmond will call in 2014 to coincide with the 700th anniversary of Robert the Bruce's defeat of the English forces at the battle of Bannockburn, is going to be very difficult for the Unionists to win. But David Cameron, desperate not to be the last British prime minister, seems privately to be taking a keen interest and is scouting actively for ways to persuade the Scots and the English that — in the old Unionist phrase — we are stronger together and weaker apart. Europe's crisis can help him make that argument.

I realise there are a good many English Conservatives who would welcome Scotland's departure, mainly because their patience with Scottish special pleading has run out. I understand the frustration but their view has long seemed baffling. Those who want "the Jocks" to hop off seem often also to be arch-Eurosceptics. They appear to have failed to work out that the morning after Scotland left the UK, with television news networks carrying images of the Union flag being lowered over Edinburgh, the loudest cheers would emanate from the seat of the European integrationist project: Brussels.