The concept of "identity" occupies a paradoxical role in our current debate.

The Yes side insists that identity has nothing to do with the referendum, while the No side talks about Braveheart on the one hand and Stout-heart on the other. It turns out that that both sides are right and wrong. Such are the perils of asking binary questions in an analogue world

On the one hand, "Scottish identity" as it was then understood was negotiated a protected status in the Union settlement of 1707: law, school and kirk. The new idea that "The Nation" might be coterminus with "The People" was literally inconceivable till the French Revolution 82 years later, when the Union indeed wobbled. ThenWalter Scott's re-stabilisation of "Scottish-ness as Street Theatre" in 1822 combined a surface of Gaelic culture with guid Scots business sense and ushered in what we now think of as the defining tropes of shortbread and yearning for a safely buried past.

On the other hand, the first (and possibly last) persuasive popular conception of Britishness as an inclusive, protecting, democratic identity came in 1945 as a specific reaction to the betrayals of "the British People" by their masters in the First World War and the Great Depression and the founding of a new nation-myth on the togetherness of the Second World War.

It is a unlikely but brilliant coalition of an imperialist dinosaur to run the war and a tough trade unionist to run the economy. Britishness as a sense is even now much more invested in the welfare state and what we used to call the post-war consensus than in any pageant of flags and military sacrifice.

This is, I believe, as true in Cardiff and Camberwell as it is true in Cumbernauld. I don't believe for an instant in the comforting myths of a uniquely couthy Scottish sociability. Where the idea of "nation as collective responsibility" is not true is in the increasingly globalised culture of the increasingly globalised elite, of whom our current rather less-than-brilliant Coalition are the local representatives. Despite the accents and the evocations of the sacrifices of the Somme, the new British elite, New Labour very much included, see the nation largely as a marketing tool, and regard its obligations of collective welfare as a tedious and anachronistic burden to be shucked off as rapidly as possible.

It was David Cameron's astonishingly (but inevitably) hollow evocation of Britishness last week that crystallised this argument for me. "Brand Britain" may come to define this campaign as much as the unfortunate leaking of the No campaign's internal cognomen of "Project Fear. (Mr Cameron's elite detachment is also why he is having such problems with Ukip, whose atavistic whining he misidentifies as grossly as he clearly does with his other white man's burden in Scotland)

What is happening in Scotland, and is beyond being fixed by any number of phone calls from our relatives, is not any resurgence of Celtic identity. Rather, this is another episode in the long and now seemingly ineluctable break-up of Britain, as Tom Nairn so presciently dubbed it, and any new sense of Scottishness is defined more by an intuition of Britishness abandoned than by any feeling of Scottishness recovered. We are not so much leaving, as I've said else-where, as we recognise that we are being left.

The identity problem on these islands is not a Scottish problem. Cultural identity has never been in question here in modern times, even as it has evolved. However, it is only since the first Scottish plebiscite in 1979 that Scotland has existed as a democratic polity, with consequences that were perhaps as inevitable as Tam Dayell always said they were. It is Britain's identity that is now being radically under-mined, and not by people with Saltires painted on their faces, but by those with Union Jacks emblazoned on their waistcoats. It is those to whom the idea of Britain still matters who are being most insulted by the Prime Minister's defence of it.