After nearly a year of waffling, Britain on Monday finally opens negotiations with its European Union counterparts about leaving the bloc, with the final outcome, due in 2019, as important as it now seems unpredictable.
During the first phase of talks, European Union negotiators are expected to go through a list of rights of European Union nationals line by line.
Anxious by mass immigration and loss of sovereignty, Britain a year ago voted to end its decades-old membership of the 28-nation bloc in a shock referendum result.
While Barnier insists on the "sequencing" of talks, so that trade negotiations can not start until probably January, finding a way to avoid a "hard" customs border for troubled Northern Ireland may well involve some earlier discussion of the matter. Three key divorce issues and trade deal Britain appears to have given in on the EU's insistence that the negotiations-first focus on three key divorce issues, before moving onto the future EU-UK relationship and a possible trade deal. Barnier said that while it was not about "punishment" or "revenge", the consequences of the UK's decision to leave the European Union were "substantial" and ought not to be underestimated.
Barnier said there was agreement that the negotiators would first look at citizen's rights, the outstanding bill Britain must pay for previous European Union commitments and the Irish border issue.
The preparatory groups will report to chief negotiators, on the table, each negotiating week. The Irish issue, long described as a priority for both, will be treated somewhat differently; avoiding a "hard border" will necessarily have to take account of how the rest of EU-UK trade will work.
The Mechanical Engineering Industry Association, known by its German initials VDMA, says that that goal of the two-year negotiating process is "damage limitation" because Brexit won't benefit either side. Britain insists that it must regain the right to control immigration and end free movement from other European Union countries into Britain.
"So, we each have to assume our responsibility and the consequences of our decisions".
"I am not in a frame of mind to make concessions or ask for concessions".
Davis, noting shared security threats for governments across Europe hours after a van rammed worshippers at a London mosque, said: "There is more that unites us than divides us".
Davis and Barnier will hold a press conference later on Monday. Yet Davis entered the talks representing a government in disarray.
In return, Davis, 68, also a mountain lover and a former reservist in the elite SAS unit, gave Barnier a signed first edition of "Regards vers Annapurna", a classic French mountaineering book, signed by photographer Marcel Ichac.
"I look forward to beginning work on that new future". I am determined." Davis channelled Winston Churchill: "The pessimist see difficulty in every opportunity, the optimist sees opportunity in every difficulty.