Bookmakers are useful political bellwethers. In the 2010 UK general election, the 1-500 offered those backing Willie Bain to hold his seat in Glasgow North East was a reflection of Labour’s Scottish dominance. Bain won more than 68 per cent of the vote. Nobody got rich.

You can now get almost even money on Willie Bain being re-elected. The odds on his Labour colleagues holding on across Scotland are longer, often much longer. The Scottish National Party (SNP) is clear favourite to win every seat in Glasgow, save Bain’s. In Paisley, Douglas Alexander, shadow foreign secretary, is on course to lose to a 20-year-old student with a fondness for Tennent’s lager.

Nothing short of an electoral earthquake is about to hit Scotland, shaking the foundations of the union that Scots voted to remain part of last September. Labour – which has won every general election in Scotland since 1955 and holds 40 of Scotland’s 59 seats – trails the SNP by as much as 34 per cent in opinion polls. The old Glaswegian quip about a monkey with a red Labour rosette being able to get elected in Scotland’s largest city will be consigned to history on Thursday.

Scottish nationalists – who currently have just six seats – will certainly smash their record Westminster return of 11, achieved in 1974. The only question is by how much.

Scotland’s referendum has transformed Britain in ways that could scarcely have been predicted a year or so ago when the long campaign for independence campaign finally spluttered into life. Support for leaving the UK was then running at about a third, as it had for most of the previous four decades. The SNP, in its second term in government in Edinburgh, was popular but the union was capacious enough to contain the constitutional ambitions of a majority of Scots.

Economic concerns

In the end just under 45 per cent of Scots voted for independence.

The biggest single factor in the No vote was economic concerns, particularly the nationalists’ unconvincing proposals for a currency union with the rest of the UK. But the referendum campaign awoke in Scots a desire for independence that many did not even realise they had. Polls suggest about half of Scots now want to leave the UK. The SNP’s stratospheric ratings are as much a product of this secessionist mood as they are of anger over Labour working with the toxic Conservatives in the bloodless, often negative pro-union Better Together campaign.

Yet the economic case for Scottish independence is, if anything, even weaker now. Rock-bottom oil prices have left the once-buoyant North Sea struggling. Scottish tax receipts are falling while public spending rises. Another referendum looks a long way off, as SNP leader Nicola Sturgeon has tacitly admitted.

What we could be facing is a decade or more of SNP dominance, amid growing support for independence, but with fears about the costs of leaving keeping the UK intact – turning Britain into a “zombie union”, not yet dead but listless, inert and lacking the vital human spark that nations, like people, need to prosper.

The lifeless zombie union could stalk this island too. Catholics will soon be in a majority in Northern Ireland. Many are attracted to the idea of Irish unification but baulk at the financial price. Northern unionists, unsurprisingly, are increasingly worried about the political journey many Scottish brethren have embarked upon. It is not hard to imagine a time in the not-too-distant future when majorities on both sides of the Straits of Moyle are bound to the union purely by economic reliance.

Resentment and dependence will grow in this indefinitely long interregnum. Governing could become increasingly difficult.

So what is the UK – or, more correctly, unionist parties – doing to address the looming spectre of a zombie union?

The answer, incredibly, is worse than nothing. The Conservatives have put party, and political expediency, over patriotism, talking up the SNP as a way to hurt Labour in Scotland. Tory home secretary Theresa May has said any role for the SNP in government would spark the worst constitutional crisis since the abdication of Edward VIII in 1936.

Labour, fearful of losing ground in English marginal seats, pledges never do a deal with Sturgeon. And so SNP poll ratings rise ever further and Scottish disenchantment grows. Bookies are offering short odds on a second Scottish referendum passing. But independence-minded punters may have to sit through many years of zombie union before they can collect any winnings.

Peter Geoghegan is the author of The People’s Referendum: Why Scotland Will Never Be the Same Again