The sign outside the new visitor centre reads simply “The Battle of Bannockburn” as though one had rolled up in time for the fight, instead of 700 years too late. The approach to the site goes through the dull suburbs of Stirling, via a northerly spur of Scotland’s patchy motorway system. In the distance is the monument to William Wallace (“Braveheart”), almost hidden by trees despite its height and bulk; and, more visibly, Stirling Castle, which was the combatants’ objective.

Behind the building is a plain which may or may not have been the precise site of the contest. There is no conclusive archaeological evidence: “You pick up a piece of iron and it’s pointed,” explains the manager, Scott McMaster. “It looks like a sword. Then you put it under the X-rays and it’s revealed as a door hinge from the 1800s. We’ve never said this is the battlefield. It’s the traditional place where Robert the Bruce planted his standard.”

Inside was a party of eight- and nine-year-olds from Bankhead Primary School in Glasgow, being shown round installations using 3D technology that is the envy of rival battlefield venues. The centrepiece is a computerised simulation of the battle, which allows for up to 30 players.

“You’re not here to recreate the original result,” the battlemaster explained to the kids. “You’re here to fight it and maybe to change it. We might have an English victory here today.”

The kids were divided up, with two-thirds being allocated to Edward II of England, which actually understates his numerical advantage, and a third to Robert the Bruce. There were immediate groans from those forced to be English, even for half an hour. This is normal.

And so battle commenced. It was somewhat confusing, which is an accurate reflection of the fog of war but also perhaps a glitch that could be improved – the centre opened only six weeks ago. The English, I felt, were overconfident; the Scots indecisive. But there was no clear advantage until the lights flashed, and the battlemaster announced that Edward had been slain (which did not happen in 1314) and the Scots had won (which did). Then the “English” kids groaned again, and some of the more bellicose boys punched the wall in frustration. This, too, is normal. “The players just get into it whichever side they’re on,” said one official.

Among the items in the gift shop were various knick-knacks that included a quotation from the Declaration of Arbroath. This was a letter sent by the Scottish nobles to the Pope six years after Scotland’s victory at Bannockburn, asking him to recognise Scottish independence. The famous quote (famous in Scotland, anyway) reads: “… for as long as but a hundred of us remain alive, never will we on any conditions be brought under English rule. It is in truth not for glory, nor riches, nor honours that we are fighting, but for freedom – for that alone, which no honest man gives up but with life itself.”

So help me, I consider myself a reasonably well-educated Englishman. But I never knew this beautiful passage. I would feel utterly ashamed, except that I suspect I have that in common with at least 99.9 per cent of the English population. Which helps explain what is happening: that on 18 September, three months after the 700th anniversary of Bannockburn, the Scots may finally turn the Declaration of Arbroath into reality.

Even more certain is that few who have remained south of the border have yet understood the mood that has gripped the Scots. The voters have not yet decided the answer to the question they must answer: “Should Scotland be an independent country?” But they are approaching it with a deep seriousness of a kind unknown among the self-mocking English.

Large numbers are telling the pollsters “Don’t Know”, as they did to the Better Together canvassers I went out with in Edinburgh South. But this was not the don’t know of a normal election, which can mean either “I hate your lot” or “Don’t care” or “I’m watching EastEnders”. You could see the voters’ brows furrowing as they contemplated the terrifying choice ahead. There is no easy option. The choice is binary, consequential and perhaps final.

Among the city’s chattering classes, there is – with more than five months to go – almost no other subject worth discussing, not even property prices. The excitement is palpable, and it is all being generated by the Yes campaign, which has more purpose, passion, unity, money and a simpler, more beguiling message. Better Together, the opposition grouping dominated by the three main London parties, has been fractured and confused.

The Westminster government’s strategy – backed up by Scottish-based companies threatening to leave – has been bluster and threat, typified by the recent shemozzle about whether Scotland would be able to keep the pound. The tone of voice was that of a parent confronting a rebellious teenager. “I’m a No voter,” one young woman told me, “and I’m affronted. Their whole approach smacks of arrogance.” (Bizarrely, the prime minister chose to make a major speech, aimed at persuading Scotland to stay, from the Olympic velodrome in London, emphasising both his own distance from this part of the realm and that London gets the best of everything.) Every time David Cameron pipes up, the Yes vote seems to tick up a point in the polls; in the case of his Chancellor, George Osborne, two.

Sir John Major, asked to make a speech in Scotland, rang the Scottish eminence and former Liberal Democrat leader Lord Steel for advice. Steel said he should come, but only if he could convey the message that the UK loves and needs Scotland, and forget the bullying. A new set of initials has started appearing in Scottish newspapers: rUK – the rest of the UK, that lot down there.

To anyone with a long memory, this is barely credible. Fifty years ago Scottish Nationalism as a political force was not much more serious than the activities of Screaming Lord Sutch. As the journalist Neal Ascherson recalled: “If you said, ‘Oh, he’s a Nat,’ it implied he was some sort of crazy eccentric. But somewhere deep in the brain of every Scotsman there was always a single cell saying ‘Wouldn’t it be great?’ It was overlaid with ‘Don’t be so ridiculous’. But it was always there.”

The concept of Scotland as a nation never faded, even when it was at its furthest from being a nation state. As Robert Crawford puts it in Bannockburns, his new literary history of Scottish independence: “Bannockburn lasted. More than anything else, the rewriting of it, and poetic reworkings of Bruce and Wallace, kept ideals of Scottish political freedom alive.” To this day, no small country on the planet evokes such obvious and distinctive associations (whisky, bagpipes, kilts, haggis, golf, Nessie, tweed, kippers, Scotch mist, the thistle …). And Scotland’s self-image was always there, through the fraught centuries of strife that tapered off first when the crowns were united in 1603 and then when the Scottish parliament allowed itself to be abolished in 1707.

“The Scottish view of the Act of Union was that it was a consensual partnership, and contractual,” says Ascherson. “Whereas the English view was that it was an Act – a decision for all time.”

For most of the 307 years since, Scottish political sensibilities were muted because there was too much going on. There was the Industrial Revolution and an empire to build, then two world wars – in all of which Scotland played a very full part. There were faint stirrings of nationalism from early on in the 20th century: Home Rule was a vague aspiration for both the Liberal and Labour parties, but the Irish experience meant there was no appetite for opening cans of worms that might turn into snakepits.

It seems no coincidence that nationalism finally gained political traction in the decade when Britain ceased to feel itself under an overwhelming external threat. The Cuban missile crisis of 1962 was the last occasion when the cold war looked like turning hot; the first significant nationalist by-election win came four years later – in Wales, oddly enough – followed by Winnie Ewing’s triumph in Hamilton a year after that.

The Scottish Nationalist path thereafter zigzagged violently, but three factors ensured that it ultimately led upwards: the massive pain caused in Scotland by deindustrialisation; the perceived failure of Labour in government, both in Westminster and Edinburgh; and, above all, the long years of That Woman, who probably did more than anyone in history to unite Scotland. In 1979, a few weeks before Margaret Thatcher became prime minister, the first referendum on devolution, offering a feeble Assembly, produced 51.6 per cent in favour, from a turnout of 64 per cent. It failed because of a Westminster stipulation that it required 40 per cent backing from the entire electorate. Eighteen years of Tory rule later, the vote was three to one.

…

No one in Scotland would now seriously argue against devolution. There is even a recognition among opponents that Scotland’s leadership is highly competent. “Alex Salmond runs quite a good government,” says Lord Steel, who is particularly impressed by Salmond’s shameless command of symbolism, which extended to arriving in a helicopter outside an Edinburgh hotel that did a remarkable impersonation of the White House.

Steel believes Salmond’s strong personality counts as a further factor that has led the country so close to independence. “Ah!” I said. “The ‘great man’ theory of history?” “I don’t think he’s a great man. He’s a clever man.”

The Scottish parliament is just as overwrought architecturally as Westminster. But as a debating chamber it is understated. With its semicircular, Continental design, it was set up for coalition, as was the complex electoral system. This was blown apart by the Scottish National party’s stunning landslide in the 2011 election, which left Salmond utterly dominant in terms of numbers as well as personality. Since the sudden death of Donald Dewar, Scotland’s inaugural First Minister, only a year after the parliament started, no major Labour figure has agreed to leave Westminster and head north, leaving the Scottish Labour party to choose five successive leaders with skills more suited to a county council.

Steel sees the push for independence as being related to the disillusionment with politics as usual that is manifest across England as well: “You could argue that Ukip are fulfilling the same role in England. But in Scotland it has an intellectual focus as well as a political one.”

When I summarised this notion, far more bluntly, to Dr Catriona Macdonald, Reader in Scottish History at Glasgow University, she almost fell off her chair. “It is so not just regional discontent. Post-union, what was left of Scottish identity was far more than just cultural mores and sentiment. There is a separate legal system that has a totally different basis to English law. There is a separate educational system that educates its children in a different way. There is a separate church without a monarchical head. Devolution gave Scotland a taste of what was possible. Post-industrial globalisation could have been very limiting. But what globalisation and the internet have done is to make small voices louder. We don’t need to go to Fleet Street to tell the world we are a wonderful country.”

There is an emphatic, often rousing, nature to pro-independence support. They have the best jokes and all the tunes and, sometimes, a slow-burning certainty: in the words of Sarah O’Gallagher, an Edinburgh lawyer: “I think we can do so much better than this.”

But although Better Together has had trouble articulating the feeling, there is passion – a quieter passion – on the other side too. I found it among the No canvassers, almost all political virgins, working the streets in Edinburgh South.

“If it were a Yes vote and I hadn’t done anything, it would have been one of my biggest regrets,” said Jonathan Deb, an accountant. “People are enslaved by this novelty,” said David Miller, a retired businessman. “But it’s not a novelty, it’s very serious.” “I really do worry,” added Alastair Gillespie, a retired maths professor, “that Scotland will become even more parochial.” Salmond’s on-off love affair with the American egomaniac Donald Trump and his controversial new golf course near Aberdeen shows just how vulnerable an independent Scotland would be to rich but dubious outsiders.

Nor is the young/old divide straightforward. For the first time in any British poll, 16- and 17-year-olds are being given the vote, the political calculation being obvious. The sixth-form vote is hard to gauge at this stage, but when Glasgow University held a preliminary mock-poll early last year, the No campaign got 62 per cent.

The circumstances of the real vote will be very different. In late July, a month after the Bannockburn anniversary and two months before the referendum, Glasgow hosts the Commonwealth Games. In terms of quality, the competition at this event is sub-sub-sub Olympic, but in terms of size it is only sub-Olympic. It has a habit of galvanising the host nation, especially if it is perceived as an organisational success (which in Scotland involves the big if of fine weather), accompanied by a decent hand of home wins. The UK nations all compete separately and if “Flower of Scotland” rings out regularly at the medal ceremonies, it will have a more than normally dramatic effect.

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The problem for Alex Salmond is that if there is a Yes majority, which not a single opinion poll has yet predicted, the majority is likely to be tiny. And 51 per cent is a very fragile, perhaps untenable, basis for independence. (Already, there are noises about a breakaway by Orkney and Shetland, a constituency which regards Edinburgh with the same suspicion as Edinburgh regards London.)

In some ways the vote has come too late. “It’s Scotland’s Oil,” was an early self-interested rallying cry for the SNP, but the North Sea’s stocks have largely gone. The notion that Scotland might be an economic “tartan tiger” has been ravaged in the past few years. Its two biggest banks, the Royal Bank and Bank of Scotland, have both been bailed out by the UK taxpayer. Even Rangers, its most successful football club, has had to be salvaged from liquidation and disgrace.

In other ways it is too early. As in the first devolution vote, the collective will is not there yet; the independence pie is still only half-baked. I am convinced that Salmond knows this and thus – deep down – does not want to win. Not this time. He would not have wanted the referendum now, but was forced into it by the extent of his 2011 victory.

“I remember him walking into parliament just afterwards,” recalled Magnus Linklater, columnist and former editor of The Scotsman. “And he stared round at the massed ranks of the SNP, many of whom I suspect he hardly knew. The look on his face said ‘My God, what have we done here?’”

I sense his best result would be a heroic defeat: anything above 40 per cent Yes, enabling him to march on Downing Street with a list of demands for “devo max”, giving Scotland a US state’s autonomy within the UK. If thwarted, he would claim betrayal and threaten another referendum (“a never-endum”), by which time his sense of grievance might have finally won over Middle Scotland. In London, which has so badly mishandled the story, this much seems to be tacitly understood.

Constitutional referendums have a habit of making voters nervy and conservative. In 1975, the British voted overwhelmingly to stay in what was then the Common Market, though they would probably never have voted to go in had they been asked two years earlier. And Australia still has the monarchy. “There is an aspect of the Scottish character that really resents the threats coming out of London,” says Linklater. “But as the campaign goes on, they will still be tucked away in the back of everyone’s minds.”

However velvet a divorce might be, there is always pain. The Tweedside town of Coldstream is a small, friendly, elderly place, just across the river from Northumberland, England’s most northerly county. The border that emerged from all the medieval conflict is strange and unpredictable and only rarely marked by anything as obvious as a river; round here, routine journeys involve regular crossings and recrossings. The Post Office ignores the whole thing: the TD (Tweed) postcode is border-blind, and the mail goes out from Coldstream to all the surrounding villages. The border, as it now exists, has almost no effect on people’s lives, their shopping patterns, their hospital appointments. A large chunk of the population is indeed English – pensioners from Tyneside and Merseyside who have chosen to retire here.

Frontier towns can do very good business, licit and otherwise: differential tax and exchange rates create all kinds of possibilities. (A few years back, when the euro rode high and the pound was low, it seemed like the whole of Ireland was pouring into Newry, just inside Ulster, to stock up.) Just by the Tweed is The Old Marriage House, which did a roaring trade as an easterly alternative to Gretna Green in the days when Scotland had much laxer marriage laws than England. But I found no one in Coldstream licking their lips (a quick poll produced 12 firm Nos and one Don’t Know), certainly not The Old Marriage House’s current resident, Bill Roue. He is an affable chap, but 81, and preoccupied with nursing his sick wife. He is also from Newcastle, and nervous: “I don’t think Scotland is big enough to support itself.” He certainly has no plans to go into the quickie-wedding business.

Coldstream is not typical Scotland, but in this complex country it is not quite clear where that might be. There is even evidence that many rural SNP voters, who in England might be Liberal Democrats, are not remotely interested in independence. On the eastern edge of Glasgow, however, is Easterhouse, the estate which replaced the old Gorbals as the epitome of Scottish hopelessness. It was here that Iain Duncan Smith, during his brief stint as Tory leader, arrived in 2002 and had what was seen as his “Easterhouse epiphany” and became concerned about poverty. Twelve years on, he is secretary of state for work and pensions and the man in charge of reducing Britain’s welfare budget.

Sandy Weddell, the long-time minister of Easterhouse Baptist Church, was Duncan Smith’s guide to the area. He still has a certain affection for his guest: “I feel IDS has been given the poisoned chalice.” In the years since, a good deal of money has been spent on the community: there are good-looking new houses with gardens generous enough to make a Londoner drool, and an innovative new arts-cum-leisure centre. The indications of deprivation are more subtle: obesity, apathy and cans of lager piling up in the open spaces. Some families are now said to have reached the third generation of unemployment.

“In Mrs Thatcher’s day it was the poll tax,” says Weddell. “I think the bedroom tax has become very similar. There’s a real sense for those on benefits that things have not just got worse but could get even worse.” Many families in Easterhouse come from the bedrock Protestant, Rangers-supporting, West of Scotland working class, where the menfolk fought the war and saw themselves as so firmly British that they helped give the Tories (aka “the Unionists”) a majority of Scottish votes in 1955. This is the sector of the population that the pollsters now detect flirting with independence. If they turn out.

Weddell told me that one of his parishioners had just walked in and announced: “I’ve had the shock of my life. My father-in-law says he’s voting Yes. I asked him why and he said ‘For the grandchildren’.”

It was a lovely sunny day with a soft breeze. Springtime in Scotland, like a politician, habitually promises more than it delivers. But in Easterhouse there was a strange sense of something that almost felt like hope.

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