A CLEAR pattern has emerged in the Brexit negotiations. British cabinet ministers and their fellow Conservative MPs fight among themselves over their goals. Eventually the prime minister comes up with a deal. But it is promptly rejected by the European Union, which suggests a different plan. And the EU proposal often prevails.

So it may prove with Theresa May’s latest idea for Northern Ireland. Her cabinet is split over two options for a future customs arrangement, to avoid imposing controls at the Irish border. Her preference is a “customs partnership”, whereby the United Kingdom would apply EU customs duties, but rebate the difference for goods that stayed in the UK. Most Brexiteers prefer a plan known as “maximum facilitation”, in which new technology, trusted-trader schemes and exemptions for small businesses would obviate the need for checks. Neither option is acceptable to the EU, neither is remotely ready and “max fac” might cost businesses as much as £20bn ($27bn) a year, say British customs officials.

Given such scepticism and the shortage of time, attention is shifting to the “backstop” option that would be adopted if neither of Britain’s preferred systems is ready. In December Mrs May promised that, in the absence of other agreed solutions, she would keep Northern Ireland in the EU’s customs union and aligned with any single-market rules needed to avert border checks. Now she proposes a time-limited extension of customs-union membership for the UK as a whole, until one of the other customs options is feasible. Yet Brussels has already rejected this idea.

Ireland was always going to complicate Brexit, for Mrs May’s objectives seem incompatible. She wants to leave the customs union and single market and be able to do free-trade deals with third countries. Yet these aims clash with the objective of avoiding a hard border in Ireland and any associated infrastructure, checks or controls. That is why the EU, urged on by Dublin, insisted that Britain had to agree to some way of avoiding a hard border before it would discuss future trade relations.

Full English Brexit

The border is more than a technical issue. Its disappearance made possible the Good Friday Agreement of 1998, which brought peace to Northern Ireland, and the development of an all-island economy. Cathy Gormley-Heenan of the University of Ulster says the true border is in the mind, not on the ground. Those who said the return of a hard border could bring back violence of the sort seen before 1998 may have exaggerated. But police in Belfast are clear that any infrastructure on the border would be seen by many as a legitimate target. So other EU borders, such as those with Norway or Switzerland, where infrastructure is obvious, are poor models.

The political situation is also fraught. Northern Ireland’s power-sharing executive collapsed 16 months ago for other reasons, but observers are in no doubt that Brexit is now the main obstacle to its reconstitution. Mrs May’s government depends on the Democratic Unionist Party (DUP) for its parliamentary majority, leading some to question the government’s neutrality in the province. Border constituencies are represented by nationalists from Sinn Fein, which refuses to take up Westminster seats. And politics intrudes south of the border too. Leo Varadkar, Ireland’s taoiseach, is accused by many unionists of being incautiously nationalist. He is under pressure from other parties in Dublin not to be too soft on Britain—and he may face an election within 12 months.

This makes the border issue fiendishly difficult. Peter Sheridan of Co-operation Ireland, a peace-promoting group, says talk of controls between north and south instantly upsets nationalists; mention of checks between the north and the British mainland does the same for unionists. Nigel Dodds, the DUP leader in Westminster, calls this an absolute red line, as he says it is for most Tories. Moreover, neither of Mrs May’s two customs options, even if they worked, would avoid all border checks. That would require alignment with some or even all single-market regulations, notably for the agri-foods that are heavily traded across the border.

Many Brexiteers accuse the EU (and Ireland) of weaponising the border to drive Mrs May towards a softer Brexit. Yet in truth the issue was there from the start. Others say a small country like Ireland cannot stand in the way of a deal. But the EU’s negotiators say this is not a bilateral squabble between Britain and Ireland, but one between Britain and the EU’s 27 remaining members. A third line from Brexiteers is that, in the event of a no-deal Brexit, Ireland would suffer dreadfully. This is true, but the EU notes that Mrs May has made few preparations for such an outcome. A few have even suggested that Ireland should copy Brexit, and follow Britain out of the EU (call it Goodbyreland). This is fanciful: recent polls put Irish support for EU membership at 92%.

So why is the EU hostile to Mrs May’s latest compromise, keeping the UK aligned with the EU on customs and single-market rules for a period after Brexit? It seems ready to offer a similar option to Northern Ireland alone, but is unhappy extending the idea to the UK as a whole. Sam Lowe of the Centre for European Reform, a think-tank, says that even a temporary sojourn in the customs union and parts of the single market without maintaining the free movement of people is seen in Brussels as cherry-picking. Mujtaba Rahman of the Eurasia Group, a consultancy, adds that the EU believes that business should have to adjust only once to Brexit. Mrs May’s plan implies at least two changes.

The EU is also aware of changing political currents in Britain. Mrs May, who has promised a white paper on trade next month, is still seen as bent on a hard Brexit. But Brussels believes there is now a parliamentary majority for staying in a customs union, and suspects one could yet emerge for the single market. That would clearly solve the problem of the Irish border.

It would also fit another Brexit pattern, which is that Mrs May’s first goal is always to get through the next meeting. She may succeed at next month’s summit, if only because its agenda is heavily charged with other matters. But the autumn deadline for a Brexit deal remains. A row at the October summit could be harder to survive.