British EU officials reduced to tears as it became clear that the Leave side had won
The EU was struggling to keep calm and carry on following the UK's shock vote to quit the bloc. In a joint statement, the heads of the EU's institutions said they would "stand strong and uphold the EU's core values of promoting peace and the well-being of its peoples".
Donald Tusk, the former Polish premier, who chairs the regular summits of EU leaders, said the bloc was prepared for the fallout. "What doesn't kill you makes you stronger," he told reporters.
The public show of unity masked a private sense of shock, devastation and uncertainty about the future that pervaded the institutions.
British EU officials were reduced to tears early yesterday morning as it became apparent that the expected Remain vote had lost out to Leave.
Commission president Jean-Claude Juncker was moved to send a message to his 32,000 staff - including about 1,100 British civil servants - to boost morale, which is at an all-time low following what they see as a rejection of their raison d'être.
"This was not our referendum, but we have to deal with the consequences," said one Commission official, who did not want to be named.
The EU is now playing a waiting game, as the UK has refused to make an official application to leave the bloc until the Conservative Party elects a new leader and the UK parliament approves the referendum result.
Until the UK legally triggers an exit, it remains an EU member, subject to the same obligations it has had since 1973 when it joined the then EEC.
EU officials tried to goad British premier David Cameron into action yesterday, saying they "expect the United Kingdom government to give effect to this decision of the British people as soon as possible, however painful that process may be".
Ireland's EU Agriculture Commissioner, Phil Hogan, also weighed in, saying it was "essential that we set in train the essential steps to bring clarity and stability to the 27-member bloc as quickly as possible".
Under EU law, it can take up to two years or more to conclude an exit treaty and only then will the UK be able to start extricating itself from EU laws and renegotiate access to the single market, which experts say could take up to a decade.
Ireland will have to battle during the talks to ensure that its "particular national interests are fully respected", which Taoiseach Enda Kenny has said is his priority.
The negotiations will be led by Mr Tusk, who now chairs regular summits of EU leaders, with input from the European Commission. The next summit will take place in Brussels on Tuesday and Wednesday, followed by a restricted meeting of the 27 remaining EU members, minus Britain.
Fine Gael MEP Brian Hayes says Ireland will need to negotiate on two fronts: with the UK, to secure the common travel area, and with the EU to protect its national interests as part of the bloc's future settlement with a post-Brexit Britain.
"The bigger issue now is our contingency plan and establishing what are the red-line issues for us," Mr Hayes said. "We need friends now in Brussels, at diplomatic and political level."
Irish diplomats, meanwhile, are reeling from the Brexit vote. They see the UK as a powerful ally at the negotiating table, particularly on banking and tax issues, and a source of knowledge on technical and complicated files that they don't have the resources to delve into.
Independent MEP Marian Harkin said of her British colleagues in Strasbourg: "We had a common understanding about lots of things, even when we didn't agree on some of the changes."