Has Boris Johnson forgotten how and why he won the Brexit vote? writes Robert Peston

During the 2016 referendum battle, I consistently said that leaving the EU would make the UK poorer, though probably not as poor in the short term as George Osborne was arguing.

But - as I always added night after grinding night on News at Ten and in a couple of Tonight films I made for ITV - there were other reasons why people might choose to Brexit, such as increasing the independent power of Parliament and the courts, or having a greater say over who can come to live and work here.

The complaint of Remainers after the election result that “no one voted to make themselves poorer” was a canard, a convenient fiction. This was to imply that only wise Remainers were privileged enough to understand the basic laws of economics.

They were patronising and wrong.

Boris Johnson met Nicola Sturgeon in Scotland earlier this week. Credit: PA

Many people voted to leave the EU aware of the likely cost to their living standards and because that was a price worth paying to make a reality of an idea they had of themselves and their country. This was an important strand in my last book, WTF.

The economic slowdown we’ve experienced and which looks set to worsen, caused largely by increasing the cost of access to our biggest overseas market, the EU’s single market, should be seen therefore as a payment for something else, for an enhanced sense of self determination, for an increase in the perceived sovereignty of the nation, for (to employ Vote Leave’s highly effective slogan) taking back control.

Here is the slightly simplistic nutshell: for a slim majority of people, the idea of plucky Britain triumphing in an unfriendly world alone, what some would see as the myth of Albion, trumped the idea of that relatively modern invention, a collegiate Europe embodied in the EU as the bulwark of a whole continent’s peace, security and prosperity.

The idea of nation has led to the defeat of pro-EU voices. Credit: PA

The idea of nation trumped whatever the EU represents. And there lay the inevitable defeat of David Cameron, George Osborne, Tony Blair, Gordon Brown, Jeremy Corbyn and all those claiming with varying degrees of enthusiasm to lead the campaign against Brexit three years ago.

They had spent most of their careers characterising the EU as a necessary evil, a pain-in-the-backside spouse with whom we couldn’t live and we couldn’t live without; it looked for all the world as though they were clinging to a marriage because of fear of being alone, not because of active joyful choice.

With the benefit of hindsight it is astonishing that Remain polled as well as it did, given that its leaders did not possess even the basic language to make the case for the EU.

The reason I am harping on about the emotive power of nationhood, which is so hard to beat in a campaign, is because Boris Johnson does not appear to have learned this basic lesson of his own triumphal Brexit battle.

In galloping towards a no-deal Brexit for the benefit of an England that voted decisively to leave the EU, he is trampling on the perceived rights to self-determination of a Northern Ireland and Scotland that each voted decisively to remain in the EU.

A pro-EU campaigner attaches a EU flag in Westminster. Credit: PA

Johnson is creating the very conditions in which Scottish and island-of-Ireland nationalism must flourish and would almost certainly trounce attachment to and affection for that other supranational construct, the United Kingdom.

I said earlier that Brexiters were aware there would very likely be an economic price for securing the other putative virtues of independence from the EU. But what matters is that the citizens in Northern Ireland and Scotland were not willing to pay that price.

And now they are being informed that the price that they don’t want to pay in any case will be a multiple of what they had been warned to expect - because they are being instructed to brace for the shock of a no-deal Brexit, rather than the managed and agreed withdrawal that Johnson assured them in 2016 was inevitable.

The frailty and fragility of supranational constructs - like the EU, like the UK - is in their very essence, that they are a collective of nations, and they can only survive by consensus or coercion.

If Johnson rips Scotland and Northern Ireland from the EU against their wishes - at the cost of a recession anticipated by the government’s own forecasters, and at the potential risk of the shattering of long-sought peace in Northern Ireland - he will rue the day.

In his pledge to unstick the UK from the EU on 31 October - no ifs or buts - he is dissolving the glue that binds the UK.

Which takes me back to where I started, that Brexit is about much more important stuff than whether the economy is set to grow a little faster or slower over the next few years; it is quite literally about who we are.