Over three and a half days, the two sides will hold detailed discussions on all aspects of the divorce treaty: protecting citizens’ rights, money, and the Irish border. Beyond these headline goals, they will discuss how to ensure a smooth transition on Brexit Day, a set of topics known as “other separation issues” where the ECJ looms large.

When Britain leaves the EU on 29 March 2019, Brussels wants to ensure that individuals and companies do not fall into a legal black hole where goods in transit fail to reach their intended destination and ongoing British court cases at the ECJ cannot conclude. Negotiators aim to guarantee, for example, that a consignment of car parts ordered before Brexit Day could still be subject to EU product rules – and the ECJ – even if it reached its intended destination after Britain has left the EU.

Yet defining the role of the ECJ will be one of the most sensitive issues of the Brexit divorce treaty, as Theresa May has vowed to take the UK out of the jurisdiction of the Luxembourg court. She also wants to ensure that any disputes over EU citizens’ rights are settled by British courts, not judges in Luxembourg.

Despite concern in Westminster that the government’s opposition to a future role for the court has limited its room for manoeuvre, three position papers published last week recommitted Davis to rejecting any continuing role for the ECJ after Brexit.

European diplomats fear the UK is continuing to box itself into an uncompromising position and are expecting it to push back strongly on the court, as both sides map out their differences in detail during the negotiations.

Davis is expected to call for both sides to “get down to business” as he arrives for the second round. Whitehall sources say he will set out citizens’ rights as his personal priority for the round, with a new push to lift uncertainty for the three million EU citizens living in the UK and one million Brits living in the EU.

“We made a good start last month, and this week we’ll be getting into the real substance,” Davis is expected to say. “Protecting the rights of all our citizens is the priority for me going into this round and I’m clear that it’s something we must make real progress on.”

Monday’s talks, however, come amid signs of increasingly serious splits within the UK government over the preferred approach to the talks, with the chancellor, Philip Hammond, complaining on Sunday that he was being briefed against by fellow ministers opposed to his pro-business focus.

Twice in as many days, newspapers ran hostile stories about Hammond from last week’s cabinet meeting, leaked by other ministers at the table. One said Hammond had urged against lifting pay restraints on what he called “overpaid” public sector workers, while another quoted the chancellor as saying driving modern trains was so easy that “even a woman can do it”.

Hammond told BBC1’s Andrew Marr show: “If you want my opinion, some of the noise is generated by people who are not happy with the agenda that I have. Over the last few weeks, I’ve tried to advance ensuring that we achieve a Brexit that is focused on protecting our economy, protecting our jobs and making sure that we can have continued rising standards in the future.”

The international trade secretary, Liam Fox, played down the idea of divisions between him and Hammond over the length of any post-Brexit transitional deal with the EU, which he has talked of in terms of months, while the chancellor has said it could be in place for years. This was “more a technical argument” and still had to be negotiated with the EU, Fox said.

Sources in Brussels were also more optimistic on the eve of the talks about avoiding a total breakdown in negotiations, after the UK formally recognised financial obligations to the EU in a written statement to parliament last week.

The prime minister had made similar pronouncements before, but the statement to MPs and peers carried weight in Brussels. Diplomats had feared a collapse in talks after the foreign secretary, Boris Johnson, caused confusion with his statement that the EU should “go whistle” for the “extortionate” sums “they have demanded”.

Discussions on the politically charged issue of the Irish border issue will be led by Sabine Weyand, Barnier’s deputy, and Olly Robbins, permanent secretary of the department for exiting the EU. These two key players will meet regularly through the week, with the aim of keeping the talks on track.

But this next round of talks is unlikely to be definitive: EU officials expect to map out their differences with the British rather than strike any final agreements.

Further talks are expected in late August and the autumn ahead of a Brussels summit in late October, where EU leaders will decide whether the UK has made “sufficient progress” on the Brexit divorce to allow trade talks to go ahead. The EU remains uncertain about whether British negotiators will be able to conclude an agreement, amid deep political divides in the government on Brexit.

“The plenary meetings [of the Brexit talks] will show us whether there is a realistic basis for agreement or whether the British government cannot move at all because of its own problems,” said Elmar Brok, a German centre-right MEP who helps coordinate the European parliament’s position on Brexit.

On Sunday, the former Tory chair Chris Patten warned that the Brexit deadlock represented one of the bleakest moments in British postwar history. “I think it’s the worst time since Suez, though maybe even worse than that because Suez was the end of an era, the end of our colonial aspirations,” he told ITV’s Peston on Sunday,

“The European Union was our replacement for that colonial role, and thanks to the calamitous errors of two Conservative prime ministers in a row, who thought they could manage the unmanageable – the English nationalist right wing of the Conservative party – we’re in this hell of a mess.”

(Published by The Guardian - July 17, 2017)