BRUSSELS (Reuters) - Dozens of British officials and their EU counterparts got the first full round of Brexit negotiations under way on Monday, bringing a quiet buzz to the European Commission’s Brussels headquarters.

Flags are arranged at the EU Commission headquarters ahead of a first full round of talks on Brexit, Britain's divorce terms from the European Union, in Brussels, Belgium July 17, 2017. REUTERS/Yves Herman

After a brief handshake and sit-down for the cameras between Brexit Secretary David Davis and chief EU negotiator Michel Barnier, the pair left the real work of the week to teams of civil servants divided into groups by topic.

Davis returned to London but will be back on Thursday, officials said, in the hope that he and Barnier can give their political endorsement to a first set of partial agreements.

Barnier’s team is known as the Article 50 Task Force after the provision of the EU treaty under which Britain has opted to quit the European Union. Numbering about 40, most are involved in the talks in the EU executive’s Berlaymont headquarters.

Officials described a bustle as negotiators and staff moved among meeting rooms scattered along carpeted corridors and up and down lifts over nearly half of the cross-shaped building’s 13 floors.

Barnier, a former French cabinet minister who much prefers to speak his native tongue, greeted Davis in English, the only language most British civil servants can work in. Though Barnier insisted French be one of the two languages for negotiations, English is the lingua franca of Brussels and will predominate.

NO NOTES

The meeting between Davis and Barnier featured just two aides each; the absence of notes in front of the British trio, compared to sheaves of papers on the EU side, sparked scathing jibes from critics in Britain who see Prime Minister Theresa’s May’s government as divided and badly unprepared.

Other meetings involved up to 10 officials on each side, getting “down to work” as Davis said, and well aware that a pressing March 2019 deadline may crimp their summer holidays.

“They have coffee,” one source said. “And cookies, too.”

The first objective is to show enough progress on a divorce package so that the EU will agree to open talks on a future free trade deal.

The three priorities are commonly referred to as citizens’ rights, financial settlement and borders with Ireland. There are also a host of other loose ends that both sides want to see tied up legally to avoid a chaotic limbo on Brexit Day in March 2019.

London and Brussels agree that some 4.5 million expatriates who live on either side of a new EU-UK border, two-thirds of them in Britain, should not lose rights they have as EU citizens.

Britain has baulked, however, at EU demands that extend to their relatives, and at having those rights guaranteed by EU judges.

PAYING THE BILL

The EU also wants London to accept a bill to cover its share of EU spending commitments made while Britain was a member. The Commission has spoken of 60 billion euros ($70 billion), though Barnier says that for now he just wants an agreement on how to calculate it. May has said only that Britain will pay if it owes something but left open the possibility that it might be the EU that pays London.

Rights and finance are being dealt with two working groups. A third is dealing with assorted issues such as what happens to outstanding EU court cases involving Britain.

Barnier and Davis’s deputies, Sabine Weyand and Oliver Robbins, are personally directing efforts to limit disruption to peace in Northern Ireland from the creation of a new EU border.

The EU timetable, which Britain has broadly consented to after failing in a bid to start trade talks immediately in parallel, sees discussions on a deep free trade pact starting by early next year and being agreed in broad outline by around October 2018 -- when the withdrawal treaty could be done and dusted.

That would give time to ratify the divorce package before Britain is out on March 30, 2019, and arrange a transition to avoid trade falling off a “cliff edge” before a full treaty to keep markets mutually open can be concluded by, say, 2021.

For now, though, the ambition is just to get through four days of closed-door talks with enough progress to show the public on Thursday.