U.K. Prime Minister Theresa May and European Commission President Jean-Claude Juncker address the media at the EU headquarters in Brussels on December 8, 2017. Virginia Mayo / AP

“Sufficient progress.”

They’re the two words both sides of Brexit negotiations have worked for months to achieve, though perhaps no one was more happy to hear them than Theresa May. After nearly seven months of negotiating the terms governing the United Kingdom’s impending exit from the European Union, the U.K. prime minister, alongside her EU counterpart Jean-Claude Juncker, announced Friday that the sides had struck a last-minute deal to satisfy the EU’s threshold of “sufficient progress”—one that addresses all the major issues that defined the first phase of negotiations and opens the way for both sides to move onto the next.

“Getting to this point has required give and take on both sides, and I believe that the joint report being published is in the best interests of the whole of the U.K.,” May said Friday at the EU headquarters in Brussels. “I very much welcome the prospect of moving ahead to the next phase to talk about trade and security, and to discuss the positive and ambitious future relationship that is in all of our interests.”

The 15-page progress report marks a stunning breakthrough for negotiations that have been defined by one obstacle after another—from the debate over citizens’ rights (May said the deal will guarantee the rights of both the 3.5 million EU citizens living in the U.K. and the 1.2 million Britons living in the EU); to the issue of how much the U.K. owes the EU to cover its existing financial obligations to the bloc (the final sum is estimated to be as much as 39 billion pounds). Until Friday, it was the last of the three major withdrawal issues—the fate of the Irish border—that threatened to derail the talks. Only after discussions that went “right into the early hours” Friday morning were negotiators able to agree to a deal that would prevent the return of a hard border between the Republic of Ireland (a member of the EU) and Northern Ireland (a part of the U.K.). Though the agreement—in which the U.K. pledged to follow the rules of the EU’s single market and customs union to prevent a hard border in the event of no deal—was praised by the Irish government, it only received cautious backing from the Northern Irish Democratic Unionist Party (DUP). That party, a partner in government with May’s Conservatives, had earlier this week threatened to veto any agreement preventing Northern Ireland from leaving the EU on the same terms as the rest of the U.K.

Though the deal has been dubbed an early Christmas present by some British lawmakers, EU negotiators were quick to point out that the Brexit negotiations are not a sprint, but a series of hurdles—and the race is still far from over. Speaking alongside May in Brussels, Juncker stressed that the joint report is not a finalized withdrawal agreement and that “we still have a lot of work to do.” European Council President Donald Tusk was similarly circumspect, noting that “the most difficult challenge is still ahead. We all know that breaking up is hard—but breaking up and building a new relationship is much harder.”

Thus far, it’s a breakup that has in many ways favored the EU. On issues relating the size of the U.K.’s so-called “divorce bill,” the scope of EU and U.K. citizens’ rights after Brexit, and the commitments made to maintaining an open border on the island of Ireland, the overall terms of the agreement appear most similar to the demands made by EU officials when negotiations first began in May. Anand Menon, the director of the independent research institute U.K. in a Changing Europe, told me this outcome was largely predictable. “2017 has gone precisely the way anyone who understands the European Union knew it was going to go,” he said. “We’ve done the sequence that the EU demanded, we offered more money than we said we would, it’s proved difficult because of a lot of legal issues—none of that should be a surprise to anyone.”

He added: “If you thought 2017 was hard, 2018 is going to be harder.”

There are two reasons for this. The first is that the focus of the next phase of negotiations—which will cover the U.K.’s transition out of the EU and its future relationship with the bloc—will likely be much more difficult. While it is known that the U.K. has requested a two-year transition period after it leaves the EU on March 29, 2019 (during which the U.K. will remain in the bloc’s single market and customs union), the conditions for such an arrangement are still up for negotiation. “No one knows how to do transition yet, which is why I think it’s going to be very, very difficult because there are legal issues that no one has quite got their head around,” Menon said. While discussions about trade could start as early as February, negotiations cannot formally begin until after the U.K. leaves the EU.  

The second reason is political uncertainty. While May appears to have weathered much of the political instability that rocked her minority government in recent weeks, there’s no telling what divisions could arise during the next phase of negotiations—or how long May will be able to withstand them as premier. “You could imagine that if she had won that election with a very big majority, that the right of the Conservative party would not be in the kind of position to dictate terms that it’s in now,” John Springford, the director of research at the London-based Centre for European Reform, told me in reference May’s failed election gambit in June. Though she called elections expecting to expand her majority in Parliament, her Conservative party instead lost the majority it had. “She would have much more authority and freedom for maneuver in the negotiations.”

With European leaders expected to formally declare that “sufficient progress” has been made during next week’s EU Council summit in Brussels on December 14 and 15, the next phase of negotiations will likely have to wait until after the New Year. And just as both sides appear to be optimistic over Friday’s deal, they too seem aware that the agreement is hardly the last word. As noted on the very first page of the joint report, “Nothing is agreed until everything is agreed”—a caveat that will almost certainly mean the return of some or all of the withdrawal issues when talks resume in 2018.

“The money, citizens’ rights, the border will come back up—this is just the warm-up,” he said. “Next year will be sort of Brexit Groundhog Day. It’ll be the same debate again, plus transition and trade.”

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