Brexit: now comes the hard part

From now on, the stakes will be higher, the politics messier and the room for fudge much smaller

European Union leaders concluded their summit in Brussels yesterday by celebrating an important milestone that moves the United Kingdom closer to the exit door. British concessions in three areas – citizens' rights, the divorce bill and the Border between Northern Ireland and the Republic – enabled the EU27 to certify that sufficient progress had been made to move the talks on to phase two, which will cover the future relationship. Guidelines for the next stage state that they can only progress as long as all commitments given in phase one are respected. This will "David Davis-proof" the agreement, in the words of one EU diplomat – a reference to the attempt by the UK Brexit secretary last week to play down pledges made by London on the future of the Border.

That will reassure Irish negotiators, who can be satisfied that on Dublin's key concerns – the retention of the Common Travel Area, the integrity of the Belfast Agreement and the avoidance of a hard border – they have commitments to which London can be held. Dublin can also take heart from the EU27's solidarity, as demonstrated by the prioritisation of Irish issues to date and the insistence that those issues will remain a distinct strand. Many Irish people will greet this moment with a mixture of sadness and relief. Sadness, in that the deal makes it less likely that the UK will reverse its senseless, self-defeating decision and stay in the EU. Relief, in that a disorderly withdrawal would be enormously damaging to Ireland, and yesterday's deal makes that prospect more remote.

Ireland must play its hand carefully. The UK will have to be pressed, but not so aggressively that it jeopardises the smooth Brexit that is in Dublin's interests

Important as this week's milestone is, however, it will count for little without a successful conclusion to the next phase. That will be much more difficult to achieve. The stakes will be higher, the politics messier and the room for fudge much smaller. A weak Theresa May will be trying to resolve long-standing contradictions in her own positions while holding her chaotic government together. The contradiction that matters most to Ireland is London's insistence that it will leave the single market, treat Northern Ireland no differently to the rest of the UK but ensure full regulatory alignment across the Border. All the signs suggest London has no idea how this will be done. On the Irish question, German chancellor Angela Merkel said in Brussels, the UK "has to tell us what it wants" so that "we can reconcile that with our wishes."

Ireland must play its hand carefully. The UK will have to be pressed, but not so aggressively that it jeopardises the smooth Brexit and favourable future trading relationship that is in Dublin’s interests. And while the EU27 showed admirable togetherness in phase one, member states’ interests will necessarily diverge once trade is on the table. That will be the test of their unity and their solidarity.