At their first meeting in Brussels on Monday, British and European Union negotiators agreed on a timetable for the Brexit talks.
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.
Those issues are Britain's exit bill, estimated by Brussels at around 100 billion euros (USD 112 billion), the rights of three million European Union nationals living in Britain and one million Britons on the continent, and the status of the border between Northern Ireland and Ireland.
Frenchman Barnier struck a firm tone as he said the timetable for Britain's divorce after four troubled decades of membership made sense.
"Today we agreed on dates, we agreed on organization and we agreed on priorities for negotiations", Barnier told a joint press conference with British counterpart David Davis. "Mr. Hammond and others ought to be trying to convince colleagues to review the decision to leave the EU customs union, as laid out by (Prime Minister) Theresa May in her Lancaster House speech in January", he added. But it must be done in a way that works for Britain ...
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The economic impact of a "cliff-edge" Brexit, alongside the failure of the Conservatives to win a majority in the general election, should lead to a rethink of the position that "no deal is better than a bad deal".
Anxious by immigration and loss of sovereignty, Britons voted last June to become the first nation ever to leave the 28-nation EU.
Shadow chancellor John McDonnell said Mr Hammond's attempts to "distance himself" from Mrs May on Brexit shows the weakness of the PM and the "disarray" the Government is mired in.
Yet that claim quickly crumbled as soon as talks began between the Tory administration and Michel Barnier of the European Commission in Brussels.
May's government said it was "confident it can achieve a bold and ambitious deal that will work in the interest of the whole U.K".
"Let's be honest, we are already hearing protectionist agendas being advanced, disguised as arguments about regulatory competence, financial stability, and supervisory oversight", Hammond said.
"So we must be clear about ours".
Most of the attention will be paid to the negotiations on the future relationship with Ireland. Our aim is to have one week of negotiations every month.