Editorial: 'Brexit moves closer but Mrs May faces a big battle'
So it is now all eyes on Theresa May, as the embattled British prime minister faces the very difficult task of selling an unpopular deal to her colleagues in the London parliament.
EU leaders have finally sealed a deal on the UK divorce terms and endorsed a general declaration fixing a framework on negotiations on the future EU-UK relationship after Brexit has happened and grace periods of transition have expired. It has been a difficult period of 20 months of talks which began in late March 2017.
But for Mrs May it may have been the easier part. Now she must overcome opposition from both pro- and anti-EU factions.
The magic number she must achieve is in or around 320 MPs out of the total of 650 parliamentary seats. But she begins with threatened defections from the 315 of her own party colleagues, and must reckon without the support of the 10 Democratic Unionist Party MPs, who have been propping up her minority government since a bad general election result for her in June 2017.
The DUP is famously opposed to the deal because it sees Northern Ireland leave the EU on different terms to England, Scotland and Wales. Like many of the Brexiteer Conservatives, their arguments defy logic as the North is treated differently inside the EU for a variety of issues, and has differentiated itself from the rest of the UK for social law topics like same-sex marriage and abortion.
But realpolitik will dictate the outcome of this one in Westminster next month. Mrs May cannot depend on some expected defections from the Labour Party's 257 MPs offset ting the loss of the DUP and her own party rebels. Neither can she hope for much from the 12 Liberal Democrats or the 35 Scottish National Party MPs.
Yet she has shown considerable political courage over the past fortnight and gained kudos from the British public as a result. It is clear she will fight this one all the way despite heavy odds against her succeeding.
The draft deal is a good outcome for Ireland in a very difficult situation not of this country's making. The politicians and diplomats who helped deliver it are to be commended.
The EU kept faith with Ireland largely because it coincided with Brussels' and the member governments' determination that the UK could not unpick the principles of the single market. But the EU, a long-time generous supporter of the Northern Ireland peace process, gave strong support to Ireland over the Border and that must not be taken for granted.
However, if this deal does not win the necessary ratification in London, it is of no practical use to Ireland. So everyone in this country will wish Theresa May a fair wind.