In the end, Northern Ireland will be the price Britain pays for Brexit

Johnson has moved quite a distance towards what has long been the most elegant and obvious solution: running the customs border down the Irish Sea

That scandalous Brexiteer image saying “we” wouldn’t be “pushed around” by Angela Merkel may be history now. The very idea, though, that anyone could think it acceptable to circulate it at all exposes something about us that our neighbours on the continent have long known: the British – and especially the English – historical experience and self-image is very different in many ways from theirs. And our view of the 20th century’s two world wars, especially the second, is a particular case in point.

There was no enemy occupation (except of the Channel Islands, though we tend to gloss over that rather quickly). And there was no defeat (unless you count the losses of Hong Kong, Singapore and Burma, which we prefer not to mention). And the retreat from Dunkirk, meanwhile, has been recast as just another glorious chapter in our island story.

Our experience of making peace was different, too. Safely girded by the sea, we did not need to contemplate the sort of compromises required of those countries with shifting land borders and more fluid populations. Yes, there was the matter of Ireland and Northern Ireland, but, again, that was different, wasn’t it?

After all, the Republic of Ireland was seen – as it still is in some quarters – as just an offshoot of Great Britain, and it only became officially a republic and a UN member after that war. As for what might in other parts of the world have been termed a civil war or a colonial war – well, as defined by London and Belfast, the conflict in Northern Ireland was merely “the Troubles”.

Both the Merkel poster and the land border issue are relevant today, as the Brexit negotiations approach their likely endgame. And they are linked, as revealing a mindset defined by both the legacy of war and the ignorance of the reality of land borders.

When Leave.eu’s Arron Banks (yes, that man again) apologised for going too far with the Merkel poster, he added – referring to the Downing Street re-telling of a somewhat fractious telephone call between the chancellor and the prime minister – that “the real outrage is the German suggestion that Northern Ireland be separated from the UK”.

It’s not clear to me that any such suggestion was made in that phone call; we have only the “spun” Downing Street version to go on. But what if there had been, even obliquely, even politely? If, say, Merkel had gently hinted that the only way to break the current deadlock was for Northern Ireland to stay in the customs union and accept EU single market rules, that would have been neither more nor less than the truth. It is the bottom line.

The Good Friday Agreement that brought an uneasy peace to Northern Ireland 21 years ago was based, as is so much successful diplomacy, on ambiguity. As neatly expressed by the pollster Peter Kellner in a recent article, it relied on the concept of one economy, two countries – something only possible because both the UK and the Republic of Ireland were members of the European Union.

Once the UK leaves – assuming it does – that accommodation will no longer be possible. The EU needs to protect the integrity of its single market; the UK government, on the other hand, has waxed lyrical about how Brexit will liberate this natural and historic trading nation to strike more advantageous deals with other countries on our own.

You can believe that emancipatory narrative if you like. But the fact of a post-Brexit trade border with the Republic of Ireland is something that cannot be fudged.

Theresa May tried to square the circle and preserve the status quo via the “backstop” so loathed by Boris Johnson and true Brexiteers. Johnson, for his part, has proposed something different: limited customs installations discreetly away from the border, with Northern Ireland continuing to observe EU regulations for agriculture and some other goods.

This would require concessions that neither Ireland nor Brussels are likely to make. Customs installations are unacceptable to Dublin, while a largely uncontrolled border is unacceptable to the EU. That Johnson proposed such a hybrid solution at all, however, only confirms how unfamiliar the British are with the nature of land borders. You either have a border, or you don’t. It’s relatively clear with the sea border, but if two countries are in different trade blocs with different regulatory regimes, the same clarity has to apply over land.

In fact – and this might need to be said very quietly – Johnson has moved quite a distance towards what has long been the most elegant and obvious solution: running the customs border down the Irish Sea. He has qualified and dressed it up a bit, including with guarantees for the Northern Ireland executive to have a regular say. And he has even managed to get the DUP onside.

Whether Johnson can or will go any further, however, is another matter. As obvious a solution as a sea border might be, equally obvious are the objections that will be raised by the UK. It is not just the DUP – nominally Northern Ireland’s ruling party – that will oppose it, but those English and Scottish MPs of a unionist persuasion who see any move towards a maritime customs border as loosening the ties between the mainland and Northern Ireland. What’s more, support for Brexit and for unionism tend to go hand in hand – at least among MPs.

Among Conservatives in the country at large, however, the picture is somewhat different. A YouGov poll in June found that, for a majority of those who responded, preserving the union came second to leaving the EU. Asked if they had to choose between the two, a full two-thirds said they would choose Brexit – even if a consequence was Northern Ireland leaving the UK.

In Northern Ireland, the picture is similar, though for different reasons. Although the DUP campaigned for Leave in the referendum and kept its place as the largest Northern Irish party in Westminster after the 2017 general election, Northern Ireland as a whole voted to remain by 56 per cent to 44 per cent – which means that some must have voted across the sectarian divide.

With demographic trends suggesting that the DUP could soon lose its position as the biggest party, the polls show that given the choice between a “hard” border with the Republic and a customs border down the Irish Sea, a small majority would plump for the latter. A “deal” between the UK and the EU including a customs border down the Irish Sea therefore should not be impossible.

Getting it through the British parliament, however, might be – at least for the time being. Because where unionists are entirely right is in their argument that any loosening of ties between Northern Ireland and the mainland could spell further separation, and lead to a united Ireland further down the line.

If that happens, it will not be Brexit that sowed the seeds so much as the Good Friday Agreement, which rendered the land border invisible and acknowledged a sense of common identity. This is how Northern Ireland came to vote Remain in the referendum, and why it could in time vote for unification. What Brexit has done is force the UK to make a choice: if it is to leave the EU, it must face the prospect sooner or later of leaving Northern Ireland behind.