It is foolish to read too much into body language, but what we saw in Dublin on Monday morning was startling. The Taoiseach was calm, clear, sure of his tone, which was neither aggressive nor ingratiating.

Boris Johnson was deeply uncertain, unable to stand still at the podium, hesitating between tones – patronisingly matey or grandly demanding? He exuded, not the confidence we would usually take for granted in a visiting British prime minister, but an unease bordering on complete disorientation.

And it is in one way hard to blame him. In the long relationship between Ireland and England, we are on radically new ground. There has never been a moment since Henry II invaded in 1171 when Ireland had more political power than its bigger, richer neighbour. And it has now.

As if to rub in this strange fact, the Brexiteers discovered on Tuesday that when they do eventually come looking for a trade deal with the European Union, they will find across the table from them the new trade commissioner, Big Phil Hogan, representing a much larger bloc that will largely dictate its terms. The natural order of things has been turned on its head.

One of the key failings of the Brexit project has always been its reliance on an old paradigm of Anglo-Irish relations. Ireland did not have to be taken into account because in the end it would have do whatever suited England.

To the extent that the Brexiteers thought at all about Ireland during the 2016 referendum, it was to suggest that any problems with the Irish Border could be solved by the obvious solution of Ireland rejoining the UK.

Nigel Lawson, chairman of the Leave campaign, suggested before the referendum, “I would be very happy if the Republic of Ireland – I don’t think it’s going to happen – were to say we made a mistake in getting independence in 1922, and come back within the United Kingdom. That would be great.”

Failing that, Ireland would simply leave the EU as it had joined in 1973, in lockstep with the British.

But in any case, in the Brexiteers’ minds, Ireland was still no more than a semi-detached appendage, economically and politically dependent on “the mainland”. They were incapable of understanding not just that Brexit would be shaped by Irish as well as by British history, but that it would empower Ireland.

There is no mystery about the causes of this shift – at least to anyone outside the Brexiteers’ bubble. Being a full and equal member of a 27-member bloc is better than being on your own.

The change is not that Ireland has become stronger but simply that Brexit weakens Britain. It means, nevertheless, that we are in new political and psychological territory. Ireland and England have developed over many centuries ways of dealing with each other and none of them really works anymore.

Strange new shapes There’s a whole array of modes – smooth condescension, raw bullying, sycophantic obsequiousness, violent hatred, chippy defensiveness, resentful hostility – that come naturally on either side. They are all now outmoded. In the great sea-change of Brexit, Anglo-Irish relations are taking strange new shapes.

Much of this strangeness consists in a kind of role-reversal. It is not just that, when we strip away the diplomatic niceties, Johnson came to Dublin essentially as a supplicant. (He needs a deal and knows he can’t get one without the agreement of Ireland.)

The evocation of bullying takes us into new psychological terrain – not of the righteous anger of the master but the self-pity of the victim This necessity is humiliating, and we have experienced over the last two years attempts at the standard response: rage at Ireland’s failure to know its place and do what it is told.

But the evocation of bullying takes us into new psychological terrain – not of the righteous anger of the master but the self-pity of the victim.

This is something much deeper – and much weirder – than a simple sense of affronted superiority. It has to do with the hyped-up psychodrama of Brexit itself, the way it imagines itself as a national revolt by an oppressed people against a foreign empire.

What is at work is not so much nostalgia for empire as a throwback to the binary mindset of imperialism, in which there are only two possible states: dominant or submissive. The normality of being one country among 28 is not possible.

If Britain is not dominating the EU, it must be being dominated by the EU. And it must therefore end this condition of intolerable submission by having its own war of national liberation. What is the nearest available model of such a revolt? Ireland’s rebellion against the British empire.

This may seem bizarre (because it is) but consider the fact that, as Ronan McGreevy recently pointed out in The Irish Times, Nigel Farage, the real father of Brexit, has on the door of his office in Brussels a portrait of his hero, Charles Stewart Parnell.

Farage told McGreevy the portrait is there “because Parnell and his party acted as the great disrupter of the UK parliament in order to draw attention to the cause of national independence”.

In this supremely self-pitying analogy, Britain (though in reality England) is in the same condition of prostration in relation to the EU as post-Famine Ireland was in relation to the UK.

Thus, Ireland did not have to be thought of as a separate problem for Brexit because, post-Brexit, England would be Ireland. As political reality gradually took hold in 2018, the less extreme Brexiteers began to imagine that it would be better for Britain to become the Irish Free State.

Circumscribed Brexit The idea began to surface in Tory circles that it might be okay to accept a circumscribed Brexit and then gradually expand it in the coming decades because this is what the Irish had done after 1922.

The pro-Brexit Conservative MEP Daniel Hannan directly compared Theresa May’s Chequers proposals of June 2018 to the approach of the pro-Treaty side in the early years of Irish independence.

“When the Irish Free State left the UK, in 1921, there were all sorts of conditions about Treaty ports and oaths of supremacy and residual fiscal payments. And what very quickly became apparent was not just that those things were unenforceable once the split had been realised; it was that everyone in Britain kind of lost interest in enforcing them.

“And although there were some difficulties along the way in the 1920s, it turned out to have been better to have grabbed what looked like an imperfect independence and then built on it rather than risking the entire process.”

In this vertiginous analogy, in the 1920s and 1930s Britain is the EU and Ireland is, um, Britain. Now, the EU is Britain and Britain is Ireland.

When the room stops spinning and vision is restored, what can be focused on is the breathtaking nature of the shift in self-image. The British are now the people against whom they themselves once unleashed Oliver Cromwell and the Black and Tans, the gallant indigenous occupants of a conquered and colonised territory rising up against their imperial overlords.

The myth of Perfidious Albion is replaced by the myth of Perfidious Hibernia In this, the Brexiteers are going Green with envy, weirdly jealous of Irish nationalism’s grand narrative of tyranny, suffering, revolt and liberation.

When Boris Johnson talks, as he has done repeatedly, of the goal of Brexit, being “independent, democratic self-government”, the suggestion is that Britain is not independent, is not democratic and does not govern itself – exactly what Irish nationalists would have said of their own country before 1922.

Once you start thinking like this, it is a short step to turning around the whole history of Anglo-Irish relations and imagining England as the victim, Ireland as the big, bad bully. The myth of Perfidious Albion is replaced by the myth of Perfidious Hibernia.

The word that is used over and over in media and political discourse about the backstop is “trap”. The Border is not a reality but a clever conspiracy – to which Ireland is a willing and vital party – against an innocent England.

It is worth noting that, in this narrative, there is another reversal of the old stereotypes. The Irish Celt was supposed to be passionate, dreamy, impulsive but conversely not much good at rational thought. The English Saxon was, by contrast, cool, calculating, wily and therefore destined to rule.

Both sides, to a large extent, bought in to this trope and even the idea of the English as innately perfidious carried a rueful admiration – they were treacherous but very good at it.

Upside-down Now, the stereotype is being turned upside-down. Johnson repeatedly evokes the idea of Brexit as a matter of passion and impulse, “courage and self-belief”. The Brexiteers, meanwhile, see Ireland as treacherously scheming to stop this romantic upsurge of faith, hope and bravery by trapping it in infuriating matters of pointless detail.

The strangest shift of all is one that is both entirely obvious and entirely unacknowledged: the erosion of English identification with Irish unionism. If Irish nationalism is the imagined model for Brexit’s overthrow of EU imperial tyranny, where does that leave the long tradition of sympathy for Irish nationalism’s internal enemies? In no-man’s land.

This fancy dress party might all be fun if the consequences were not so serious The Conservative and Unionist Party is becoming neither. In a poll taken during the leadership election that brought Johnson to power, 59 per cent of Tory Party members said they want Brexit to happen even if it means Northern Ireland leaving the UK and joining a united Ireland.

This finding is very similar in surveys of Leave voters and Conservative voters. When Farage wants to be Parnell, and Johnson poses as the leader of a colonised little nation striking out for independence, who wants to be Edward Carson?

This fancy dress party might all be fun if the consequences were not so serious and if the mixture of emotions was not so unstable.

In 2011, when Queen Elizabeth visited Ireland and performed an exorcism on Anglophobia by acting out a recognition of equality, it seemed that Anglo-Irish relations had become what they had never been: normal. Decades of working together in the EU and on the peace process had worn away the legacy of condescension on the one side and defensiveness on the other.

But neither of those joint experiences matters to the Brexiteers. They approach Ireland instead though a strange swamp of contradictory impulses: rage and envy, thwarted superiority and indulgent self-pity.

Ireland cannot afford to reciprocate. There is far too much at stake to take any pleasure in the bizarre reversals we are experiencing. But it may be quite some time before we can hope to return to the apparently settled normality of 2011.