WITH the SNP being besieged with a number of accumulating woes, very senior Unionists are beginning to believe that Scotland may finally, at long last, have reached “peak Nat”.

After 22 consecutive polls giving the Yes campaign the lead, the last six have placed the No campaign ahead with don’t-knows as high as 14%.

Political fortunes change, sometimes quite quickly; it’s only a matter of time.

Now Unionist tails are rising, Boris Johnson is trying to lift his eyes beyond Covid to a bold vision of what he believes can be a new, improved Britain beyond Brexit.

Whitehall insiders stress how the strategy to reverse the drive for Scottish independence is not with teams of pointy-headed advisers, drawing up clever political wheezes to wrongfoot SNP high command but, rather, with shovels-in-the-ground projects, so voters can see the so-called “Union dividend” for themselves.

This is what Alister Jack means when he mentions “real devolution”; code for bypassing Holyrood and engaging with local organisations to build local projects for local people.

It is understandable Nicola Sturgeon rages, regarding this as a shameless power-grab under the devolution settlement. Because it is.

But, unashamed, the UK Government’s argument is 1) the SNP, despite its rhetoric, does not believe in devolution, ie sharing power, because it wants to have it all in an independent Scotland and 2) it has used the devolved settlement not to improve Scots’ lives but merely to further the push for independence.

This week, the mother of all shovels-in-the-ground projects was highlighted with the UK Government announcing that a multi-billion plan for a bridge or tunnel across the Irish Sea would be scoped by two top civil engineering experts.

It may come as a surprise to some that a plan for a “fixed link” across the Irish Sea is not new.

As long ago as 1800 when the Act of Union between Britain and Ireland came into being, William Pitt, the PM, had a doozy of an idea to build a bridge between Holyhead and Dublin to cement the new relationship, quite literally.

A century later, architects were eagerly drawing up grand designs not for a bridge but an undersea tunnel in the North Channel between Scotland and Northern Ireland.

In 1897, when a Tory MP in the Commons enquired about the project, Arthur Balfour, First Lord of the Treasury, told his colleague dryly: “The financial aspects...are not of a very promising character.”

Yet the dream persisted.

MPs throughout the 20th century continued to broach the possibility of a tunnel across the Irish Sea.

While the Dublin Government insisted it would not be economically viable, the idea was revived by Northern Ireland’s Democratic Unionists, who even made a feasibility study into a tunnel or bridge a precondition of their support for the UK Government in the event of a hung parliament in the 2015 General Election. Thankfully perhaps for David Cameron, the Tories won a majority.

But it was when the idea was resurrected by an academic three years later that Boris’s imagination suddenly took flight and he insisted a bridge would create a “Celtic powerhouse” fuelled by increased trade across the water.

By the time he became PM in summer 2019, Mr Johnson was firmly committed to exploring the fixed link idea, hence this week’s scoping plan in the Union Connectivity Review.

However, of the two options a road bridge seems the unlikeliest.

As one engineering expert pointed out maintaining a 28-milelong bridge would be an even greater task than building it. Costs would be “eye-watering,” he warned.

And to put the scheme into context, a Celtic Crossing on this scale would make it the second longest road bridge in the world after the Bang Na Expressway in Bangkok. It cost £720m back in 2000.

So, a tunnel then?

This project would be comparable in length to the Eurotunnel but it has been pointed out it would have to be diverted to avoid Beaufort’s Dyke, a 1,000ft deep trench, which is loaded with more than 1m tonnes of munitions dumped there from the days of the Second World War.

The Eurotunnel cost £4.7bn to build; a new version would cost at least three times that today. So, a Union Tunnel would be one of the biggest infrastructure projects ever to be built in the UK. From the PM’s point of view, it would solidify the “wonderful Union” and be part of his legacy alongside Brexit.

But will Britain, and more specifically Scotland, buy into the Unionist vision of a Strategic Transport Network with better road, rail, air and sea links, making the UK a simpler place to get around.

On Wednesday, the Scottish Secretary snapped that the Scottish Government was “pathetic” for not engaging in the connectivity review because its title contained the dreaded word ‘Union’ while Michael Matheson, the Scottish Government’s Transport Secretary, huffed that transport was a devolved issue, dismissing the fixed link idea as Boris’s “vanity project”.

While some people will admire the PM for his Panglossian outlook, others will feel the idea of a Union Tunnel will simply go the same way as those much-loved flights of fancy: the Boris Island airport hub; the garden bridge across the Thames and le grand pont to la belle France.

All of which have been quietly filed away in a distant Whitehall drawer under B for bonkers.