The UK will leave the EU at 11pm on Friday night but that is not the end of Brexit, far from it. Boris Johnson is insistent that a trade deal can be negotiated with the EU during the next 11 months so that the divorce becomes final on December 31. That is an incredibly short period of time to hammer out a complex series of agreements.
aoiseach Leo Varadkar has warned that the EU may well play hard ball during the negotiations and that the 27 member states hold the upper hand.
None of that, of course, makes any difference to the Prime Minister who respectfully but determinedly begs to differ. Boris is nothing if not a man who likes to get things done - no matter how.
And that is why unionists fear the forthcoming negotiations. EU chief negotiator Michel Barnier told an audience in Belfast last night that frictionless trade between Northern Ireland and the rest of the UK is not possible because the province will follow EU rules on agricultural and manufactured goods, while the rest of the UK will not.
The net result will have to be checks at Northern Ireland ports - the so-called border down the Irish Sea - a totem which makes unionists afraid that the Union is being weakened.
Mr Barnier was quite blunt in his warning that Brexit would have some consequences which would have to be managed.
Those consequences will not become clear until the trade negotiations have reached a fairly advanced stage, but it is clear that concessions on both sides will be demanded and that makes it imperative that relationships between the UK and EU do not deteriorate. The hope has been expressed that they will improve.
There does seem a genuine sadness among EU states that the UK has decided to leave.
That is partly because the EU exports more to the UK than the reverse trade but it is also because a major partner in trade, security and diplomacy is cutting itself adrift.
The new Northern Ireland Executive has rejected the UK-EU deal but that is ritual rather than having any effect. Instead ministers will have to concentrate on how to make Brexit work as effectively as possible for the province.
The all-Ireland economy has been safeguarded and guaranteeing free entry to the EU on certain goods is a bonus worth expanding on. We may have voted against Brexit but it might just work to our benefit in at least some respects.