Shrill, leaderless and fizzing with all the emotional power of a bank statement. That is the abridged verdict on the campaign to persuade Scots to vote against independence in September’s referendum — from its own friends. As polls start to make secession look plausible, if nothing like probable, unionists are urged to state a more romantic case for the UK than the logistical ordeal of undoing it.

They should resist. There is no evidence that sentimental unionism would be outperforming this hard-headed version. Better Together, the pro-UK campaign, should certainly curb its apocalyptic tone but its line of attack is probably the best available. Scots who are emotionally committed to the union will vote for it. Scots who are emotionally set on independence will vote that way.

This referendum was always going to be settled by the undecided, who are not tugged by their souls one way or the other. Exposing them to practical doubts is only sensible. Those doubts, about an independent Scotland’s currency and EU status, have just turned out to be less intimidating than expected.

Going all mawkish now about “300 years of history” would suit only Alex Salmond, the nationalist first minister who, on top of his cold ingenuity, can out-emote anyone.

Unionists should stop fretting about their campaign. Their predicament is much worse than that. Whatever happens in September, it takes a feat of self-deception not to see that Scotland has become a very different political culture from England, if not also the rest of the UK, and that the future is one of gradual estrangement.

For greater autonomy

This point is best made by reiterating two features of the referendum debate that the people have come to accept as somehow normal. First, this is a debate in which even the staunchest unionists believe that Scotland will be given greater autonomy if it votes against independence.

Some actually want their campaign to tout this offer as a “positive” reason to vote No. Why risk separation, so this supposedly stirring message would run, when you can have something similar under the safety blanket of the UK?

When even unionists accept that the union will become looser, its future is insecure. The next round of powers for Edinburgh will be followed by another, and another after that. Former UK premier Tony Blair once boasted that he has no reverse gear — neither does devolution, his main constitutional reform as prime minister. It is a process, not an event, and if its destination is not independence, it may be “devo-max”.

According to February’s Scottish Social Attitudes Survey, this arrangement, which would empower Edinburgh on virtually everything outside foreign and defence policy, is the most popular.

If it eventually comes, it is hard to see how MPs with Scottish constituencies could hold high office in Westminster or even vote on much legislation there, for their decisions would affect every part of the UK except the nation they represent.

And these are mostly MPs of the left. Without them, the Conservatives could aspire to command the rest of the UK in near-perpetuity, unless Labour moved right to win more votes in England. This is the other feature of the debate that is nothing like as benign as we treat it. Prime Minister David Cameron has largely delegated the unionist campaign because he rightly fears that interventions from a Conservative (and English) prime minister would set back the cause.

So many people on all sides accept this as common sense that the dark implications for the UK are missed. So it is worth going over again: The prime minister of the union cannot front a campaign to preserve that union because he belongs to the wrong party, a fact aggravated by possession of the wrong accent. This is extraordinary.

Loathed

Major figures in the unionist campaign confess that their prospects hinge on how likely another Tory-led government looks in Westminster by the time of the plebiscite, so loathed is the party up there.

The Tories’ nugatory presence in Scotland has become a line of comedy, but the joke is on the future of the union.

The most popular party in England, which accounts for 84 per cent of the UK’s population, cannot get a hearing in Scotland, which accounts for 8 per cent, and is denied a majority in Westminster because of it. This is the Tories’ own fault; parties are accountable for their own performance.

Nobody, however, can look at this structural lopsidedness without fearing for the stress it puts on the union, or wondering whether the political gap with Scotland is actually bridgeable.

Scottish public life is growing so unlike England’s as to already resemble that of a separate state. Wonderfully, Salmond can call for more immigration and live to tell the tale. No Westminster politician would try. Less wonderfully, he can espouse the kind of economics that would cause much of England to check that it was not 1975.

This disparity is not going away. The unionist campaign is a footling concern next to the deeper unionist plight.

Independence may be averted in September but the trend of history is unmistakable.

— Financial Times