Nearly exactly a year after Britain's seismic referendum to leave the bloc, the EU's chief negotiator, Michel Barnier of France, welcomed his counterpart David Davis with a cheery handshake at the European Commission in Brussels.
The terms of reference state "for both parties the default is transparency" and that it is for the side providing any information to state whether it should remain secret.
Talks are expected to stretch around 16-18 months, with Barnier insisting on sticking to the EU's priorities and negotiating the "divorce bill" before opening up talks on future trading.
Davis, taking up the historical theme, quoted British wartime leader Winston Churchill. "The optimist sees the opportunity in every difficulty". "And so bridging between Churchill and Monnet I am certainly a determined optimist".
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.
"We must first tackle the uncertainties caused by Brexit", Barnier said, citing the rights of European Union citizens in Britain and the possible impact on the open border between Northern Ireland and Ireland.
With discontent in Europhile Scotland and troubled Northern Ireland, which faces a new European Union border across the divided island, Brexit poses new threats to the integrity of the United Kingdom. The move backfired, May lost her Conservative majority in the vote and has been fending off critics of her leadership ever since.
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.
"When we eventually get to the stage where the council decide we have made enough progress, both sets of dialogue will continue, including free trade".
Britain kicks off Brexit negotiations with EU
You also have to look at what accidents might befall you, falling rocks. "We have taken the first, critical steps together". The two sides are expected to meet monthly until March 2019, when Brexit is due to happen.
A bigger problem may be for British negotiators to resolve what trade relationship they want.
While "Brexiteers" like Davis have strongly backed May's proposed clean break with the single market and customs union, finance minister Philip Hammond and others have this month echoed calls by businesses for less of a "hard Brexit" and retaining closer customs ties.
The bloc has expanded steadily since first formed as the European Economic Community in 1957 by France, West Germany, Italy, the Netherlands, Belgium and Luxemburg.
"The most important thing I think now is for us to look to the horizon", said Britain's Foreign Secretary, Boris Johnson, ahead of a meeting with other foreign ministers in Luxembourg "Think about the future, and think about the new partnership, the deep and special partnership that we want to build with our friends".
Anxious by immigration and loss of sovereignty, Britain voted a year ago to end its four-decades-old membership of the 28-country bloc - the first state ever to do so.
Davis was heartened by the spirit of the talks, during which the negotiators, both interested in mountaineering, exchanged a walking stick and a hiking book.
"It is not fair to say we have set it aside, far from it", said Barnier, reassuring journalists that him and Davis have spent a lot of time talking about this issue already this day.
Both sides acknowledged the clock was ticking, with the date for the UK's departure from the European Union fixed for March 2019.