Henry Hill is a British Conservative and Unionist activist and writer. He is also editor of the non-party website Open Unionism, which can be followed on Twitter here.

It has happened at last. The Scottish referendum has been inescapable in the media north of the border for months – to the extent that Scotland was being gradually squeezed out of this normally referendum-light column. But one poll showing Yes in the lead has breached the dam, and now the issue is inescapable down here as well.

The overall mood is one of surprised panic. For the first time, the dissolution of the Kingdom has become a tangible, concrete possibility. Lots of people who had not previously given the issue a lot of thought are waking up to the fact that in just over a week their country could cease to be.

Quite how the No campaign has managed to throw a 20-point lead in four weeks is hotly disputed. There are plenty of theories: that the No campaign is being too negative; that the SNP have a monopoly on the ‘heart’ side of the struggle; and so on. But these things have been common criticisms of Better Together since it was set up. The idea that it all hinges on Alistair Darling’s poor performance in the second debate seems a bit of a stretch.

One genuinely new pro-separation argument to crop up has been the notion that the oil industry is conspiring with unionist politicians to conceal the existence of a huge oilfield in Scottish waters, containing wealth enough to fund the SNP’s increasingly ridiculous blend of promised tax cuts and spending increases. I hesitate to lend this much weight because to accuse a Scot of changing their vote on the basis of such a notion is to reveal a very low opinion of them indeed.

Another type of theory is that this last-minute pinch is the result of long-running flaws in the Unionist campaign coming home to roost.

Some, including the Daily Telegraph’s Dan Hodges, pin the blame on Labour. These attacks are not without weight: many Labour people appear totally incapable of setting aside partisan political enmity to partake in a genuinely cross-party campaign, and it is reportedly Labour voters who are being lured towards Yes by Alex Salmond’s illusory social-democratic nirvana. In the longer view it was Labour who designed our present, unstable constitutional settlement and who left second-rate political talent to face off against the SNP in the Scottish Parliament.

Perhaps most seriously, it was Labour who for so long played into Salmond’s hands by casting the Conservatives as an ‘un-Scottish’ force and devolution as a weapon against them.

Others argue that this razor-edge result vindicates those who called for ‘Devo Max’ to be a ballot option. It is easy to see why they feel this way, especially in light of the recent and rushed announcement of an ironclad pledge of yet ‘more powers’ by the unionists ahead of the vote. Gordon Brown has even disinterred the phrase ‘Home Rule’, which ought to send chills down the spine of any unionist with an ounce of historical perspective.

I personally disagree with that analysis, and hope to put the case against a pre-referendum promise of powers in full in another article. Of the ‘long term causes’ theories it also convinces me less than the Labour one – why would the lack of more powers become a problem in the final month?

Regardless of the reason, the poll has upended Better Together’s tactics. In addition to the aforementioned rush to more powers, the leaders of all three of the main national parties are abandoning Prime Minister’s Questions tomorrow to make a joint appearance north of the border. Nigel Farage has also grasped the significance of the moment, and his own Rally for the Union, planned for Friday night, is now free to attend.

As for the overall impact of the poll on the final result? You can make the case both ways. Obviously the narrowing of the gap to the razor’s edge is very much to Yes Scotland’s advantage. But they could perhaps have done with it happening slightly later in the campaign, for they risk following their Quebecois forebears in 1995 and peaking too soon – for this poll has sent a bolt of lightning into unionism which I had feared was never coming.

North of the border, this panic (not the poll itself, but the response) is a greater marginal boon to the Union than to its enemies. One of the separatists’ main assets has always been a more motivated activist and voter base. One of Better Together’s principal fears has been that low turnout would allow the Union to slip through their fingers because come hell or high water, the Nats would vote. It is not for nothing that “There is no room for complacency!” has been the unionist rallying cry these last months.

As a result of their comparatively under-motivated electorate, the unionists have more to gain from anything which energises the voters – and this poll is far more likely to get a complacent unionist to the polling station than an apathetic separatist for the simple reason that there are far more of the former.

The other big silver lining is that this poll has brought home to voters outside Scotland just what is at stake. Today I saw Carwyn Jones, the Welsh First Minister (about whom this column cannot make up its mind) campaigning in Scotland on the television, and the case for the Union being made on the front page of the Evening Standard. The Spectator, which in fairness has had a very good line on the Union for as long as I can remember, is dedicating a front page to letters from non-Scottish Brits making the case for the Union (get yours in before noon).

It’s not up there with the equivalent constitutional crisis over Ireland, where even the local elections in the town of Chorley (where I served a stint on a local paper) were completely dominated by where the candidates stood on Irish Home Rule. But it is a welcome sign that the rest of the British are finally alive to the fact that it is their country on the line next week – and after all, it was the ‘Rest of Canada’ who turned things round in Quebec.