Even in the eighteenth century and early nineteenth centuries, there were those who feared that British identity was too dependent on recurrent Protestant wars, commercial success and imperial conquest, and that more thought and attention should be devoted to consolidating a deeper sense of citizenship on the home front.

Linda Colley, Britons, Forging the Nation 1707-1837

Britain has only ever existed in the face of existential threat. The BBC’s historical dramaCastles in the Sky, aired last Friday, provides a timely illustration of this.

The film follows the endeavours of a group of mavericks led by an eccentric genius. They must take on the establishment in order to convince them – despite the odds and their lack of received pronunciation – that their new invention can give Britain a strategic edge in the coming war with Nazi Germany.

That after all these years of unity Eddie Izzard still can’t pull off a convincing Scottish accent is perhaps not surprising. It mars what would be an otherwise solid performance as the Scottish born radar pioneer Robert Watson-Watt.

This is not really a film about British ingenuity, eccentricity or pluckiness. It’s about overlooking differences and responding to a threat. Incongruous newsreels of Hitler and his followers blare in at regular intervals. We must not forget the barbarians at the gates that our cross section of home nation whizz kids (including the obligatory comedy Welshman) must race against time to defeat. The penultimate scene takes place at RAF command and control with the Luftwaffe on the horizon. As our hero is ushered out and denied his moment of triumph by his superiors, victory ensues and the institutions of class and bureaucracy that are mocked throughout are validated. We’re archaic, we place class above ability, says the film: but in comparison to the alternative…

The narrative stops there.

Union occurred in turbulent times. Between the ancient rivalry between France and England and the European wars of religion between Catholic and Protestant, it was widely seen as a creature of necessity rather than desire.

Today, we learn that an existential threat is causing consternation in Whitehall once again. As a result Britain is being taken down from the attic, dusted off and made ready to be presented to the world as a functioning, cohesive country. In fact, so dusty is this concept itself, that it assumes that it is still fighting its last opponent. That fascism is absent turns a politics easily mistaken for parody into farce. Without a beastly threat from the continent to oppose, Britain is at a loss when asked to provide a rational definition of why it should continue to be a nation-state. Its traditional roles as religious protector, market facilitator and national provider, are all increasingly distant memories in the twenty-first century.

In the wake of two incendiary YouGov polls showing massive swings to Yes, a vast array of policy makers and commentators have woken up, from a deep slumber, to find the ‘Scottish question’ staring them in the face. Haltingly, they’ve realised that this is not, in fact, a matter restricted to Scotland, but one about the future of the Union itself.

In one of the most reactionary articles ever published by a British broadsheet, Will Hutton has called for a Federal structure for the UK to be laid out before voters as soon as possible. Why? Not because it’s a good idea per se, but rather to fend off what he describes as ‘the death of the liberal enlightenment before the atavistic forces of nationalism and ethnicity – a dark omen for the 21st century.’ Britain must again adapt to save itself from the other, in this case Scottish democracy. Federalism, like Watson-Watt’s radar, is needed to save British society from oblivion.

Britain’s finest hour is a rare example of authentic national pride at a UK level. Though it often obscures the multi-national effort that was required to defeat Nazism, the act of standing alone still rings true for many. The problem is, that Britain, uniquely, did not have to rebuild its national institutions after the war. Instead they remained heavily centralised: a legacy that may have led to the rapid unravelling of the post war settlement. An attendant cult of sacrifice ensures that it is not simply an abstract ‘togetherness’ that hallows Britain, it is the very real parameters of Churchill’s rule that still provoke widespread political nostalgia.

Today, the problem for Britain’s elite is more prosaic.

The concept of a country becoming independent from London is far from unprecedented. On the other hand, the simultaneous reconstituting of a national identity, the renovation of an archaic, un-written constitutional structure and its transformation into a modern one, is a tough call on a ten day time scale. Instead, at long last it may have to realise that is a regional not a global actor. A unique figure in a crowd of nations: not a solitary and superior exception.

In contrast Scotland has, since at least the 1980s and the Constitutional Convention, openly discussed how it wants to be governed. This process has been defined, not by a febrile nationalism, but by a calm and considered desire to make it new. That is why the parliament that legislated for the referendum was conceived at its birth as a modern institution drawing on European models.

Scottish independence has never been inevitable: its greatest strength stems from that knowledge. The problem for Westminster is the opposite. Even after devolution, cultural and economic centralisation continued apace at a British level. This has resulted in a campaign for unity that has refused to see this issue as anything other than a narrow, peripheral and uniquely Scottish concern.

With the exception of some notable voices on the left in England, until now, few have noticed that the matter of where power lies and who wields it is a common concern. A collective, pan-British alternative to Westminster cannot now appear on the table. Such an option would not only mean reviving the entire concept of Britishness, as a tangible project with a future, but also throw a two year long campaign for the union into reverse gear for its final ten days. I’m no strategist: but clearly neither option is desirable.

As it happens the more powers issue was supposed to have been dealt with. The momentous occasion last month involved the leaders of each Scottish branch of the unionist parties, and consisted of a bland statement on a clip art medieval scroll.

Are we to expect another scroll (perhaps on vellum this time) bearing the names of Milliband, Cameron and Clegg this week? Or will the leaders go further and chisel the somewhat vague promise of ‘a stronger Scottish Parliament in a stronger United Kingdom’ on to the Stone of Destiny?

The rest of Scotland’s now intensified conversation with London, we are told, will centre on what kind of self-government Scotland wants. Which is odd, because that is what the Yes campaign has been talking about all along. Simply put, until the polls narrowed even countenancing the prospect of authentic constitutional reform was too radical a step for British politicians to contemplate.

All of this provides an extreme contrast with the tone prevalent in previous weeks. Remember front pages screaming about a growing hostility to the current Scottish political settlement? The English people, according to those poll findings, will insist on punitive measures either way. If this popular mood is tapped into: currency sharing will be blocked in the event of a Yes and Scottish spending will be cut in the event of a No.

If that happens, any offer of more powers will first have to take the temperature of what such polls claim is an English electorate hostile to the notion of ‘special treatment’ for the Scots. With the exception of the chronically declining Liberals, there is no party in Britain with any interest in the concept of federalism, the only rational or political sustainable alternative to independence.

For the Better Together coalition this awkward reality displays itself in its stuttering responses on the future, its fixation with pride and Scottishness and its inability to mobilise support. Scotland as a polity is an issue that has to be resolved, a political folly in the landscape that many thought could be made to conform.

In defending Britain, they have had to conjure up the phantom of ethnic nationalism to give substance to the myth of Britishness itself. Today the notion that 47-51% of the population could be under the sway of some new darkness is beyond absurd and even the often vivid imagination of British reaction can’t escape this.

The truth is that the union does face an existential threat from Scottish ballot boxes not marauding invaders or the forces of darkness. It may be compelled, as a result, to find a narrative that rests on something deeper than the goal of deeply flawed continuity. It must try and think of itself as something more than a polity brought together in times of crisis and at royal occasions.

For the union is not at an oppressive yoke from which Scotland must escape. Rather it is a set of institutions that have run their course. To build new structures, after decades of consideration, is not an act of narrowness or desertion. We have simply moved beyond a Britain that forgot, a long time ago, how to speak to the future of all of its people in unison.

In the nineteen seventies Tom Nairn’s Break up of Britain famously identified ‘Ukania’ as an anomaly in Europe. A nation-state held together by a hereditary monarchy rather than popular sovereignty.

In these final days, we must remember that it is not Scotland that is the problem here. Rather it’s the constitutional curio that is the UK. It has never had a fresh start: a break from the symbolic and real world of privilege that it stems from.

That time has come. If this edifice is indeed crumbling, that long overdue act of starting again will begin in earnest in ten days time. If real solidarity can still prevail in these isles, the results could be transformative in all corners of this problematic entity called Britain.