With the clock ticking on Britain's EU membership, the bloc's leadership vowed unity while in London the government was set to begin the arduous task of disentangling itself from Brussels.
"This is a moment to unite," European Commission head Jean-Claude Juncker said on Wednesday, hours after Britain formally started procedures to end its 44-year membership of the EU.
With just two years foreseen for negotiations, Juncker said the rights of EU citizens will be top of the agenda.
Settling Britain's exit bill -- estimated by the Commission to be 60 billion euros ($64 billion, £52 billion) -- will also be a priority when talks get underway, expected mid- to late-May.
But even before the negotiations start, Britain on Thursday will begin the monumental task of incorporating EU legislation for when the divorce is finalised.
Speaking in parliament on Wednesday, Prime Minister Theresa May said that was important "so that on the day we leave everybody knows those rules still apply and everybody knows where they stand".
The government will publish a "white paper" policy document on Thursday outlining its plans for the legal overhaul, which for better or worse will give MPs the opportunity to amend the laws as they are brought under the national system.
Meanwhile Juncker will meet in Malta with EU President Donald Tusk, German Chancellor Angela Merkel and Spanish Prime Minister Mariano Rajoy.
- 'We already miss you' -
Tusk bid farewell to Britain on Wednesday, after receiving the British government's divorce letter triggering Article 50 of the EU's Lisbon Treaty -- the exit clause.
"We already miss you," he said.
Merkel called for "fair and constructive" negotiations, while dismissing Britain's wish to have exit negotiations run concurrently with talks on its future relationship with the EU.
European stock markets closed slightly up Wednesday, but dealers said investors had largely "priced in" Brexit already.
Britain has until October 2018 at the latest to come up with a draft divorce plan, according to the Commission's Brexit negotiator Michel Barnier.
While May asserted in January that "no deal is better than a bad deal", in her Brexit letter she adopted a more conciliatory tone and called for Britain and the EU to "work hard" to avoid failure in the negotiations.
The cliff edge scenario of Britain leaving the European bloc with no deal has alarmed business leaders, who have also emphasised the need for a transitional arrangement to allow for the divorce deal to be gradually implemented.
The European Parliament's chief Brexit negotiator, Guy Verhofstadt, said such a transition period should be limited to three years.
Tusk is due to issue draft "negotiating guidelines" on Friday and leaders of the 27 remaining EU countries will hold a special summit on April 29 to rubber stamp the plans.
- 'A magnificent moment' -
While the bloc has tried to show a united front in the face of Brexit, celebrating the EU's 60th anniversary earlier this month, in Britain the prime minister is struggling to unite her own country.
Britons last year voted 52 percent to 48 percent in favour of Brexit, leaving the country bitterly divided with tens of thousands of pro-EU protesters marching in London on Saturday.
The referendum result has also led to a resurgence of Scotland's independence campaign, after Scots voted to stay in the EU but were outnumbered nationwide.
"Dear Donald Tusk, We'll see EU soon" read Thursday's headline of Scotland's pro-independence newspaper, The National.
The Telegraph, meanwhile, described Brexit as "A magnificent moment" on its front page, quoting Foreign Minister Boris Johnson who played an instrumental role in the leave campaign.
"We have every reason, in reality, to be brimming with confidence," Johnson wrote in the newspaper.