While a last-minute deal would avoid the most acrimonious ending to the Brexit saga, the UK is heading for a much more distant relationship with its biggest trade partner than with almost anyone expected at the time of the 2016 Brexit vote.
Britain and the European Union are expected to announce a Christmas Eve trade deal after ten months of Brexit talks dragged out over yet another late-night session.
The two sides had hoped to unveil the accord on Wednesday, and the front pages of several British newspapers already proclaimed victory for Prime Minister Boris Johnson.
But EU member states had a number of questions about the text and cross-Channel diplomacy continued through the night, with Johnson and Commission chief Ursula von der Leyen expected to announce a breakthrough shortly after dawn.
An EU source told AFP that "if all goes well" the two leaders should talk by phone at 0700 GMT to seal the agreement.
"It will hopefully be an early start tomorrow morning," European Commission spokesman Eric Mamer tweeted just after midnight, advising reporters and diplomats alike to grab some sleep as the finishing touches were applied.
Several hours earlier, European officials had confidently told journalists: "We are in the final phase."
#brexit work will continue throughout the night. Grabbing some sleep is recommended to all brexit-watchers at this point. It will hopefully be an early start tomorrow morning...— Eric Mamer (@MamerEric) December 24, 2020
But diplomatic sources said member states, in particular France, had wanted the Commission to go back to the British camp to seek specific guarantees on parts of the accord.
The British pound and Asian markets were rising on the expectation of a deal, and a French government source said UK negotiators had made "huge concessions" on fisheries -- the key sticking point as the clock ticks down to Britain's departure.
The last-gasp deal, if it is confirmed, would come just days before Britain is set to leave the EU's single market at the end of the year, sparing the two sides from trade tariffs.
A deal, which would still need to be translated and tidied up by lawyers, could be approved provisionally before the cut-off date and then scrutinised by EU lawmakers in the new year to avoid a cliff-edge.
When the UK shocked the world in 2016 by voting to leave the EU, many in Europe hoped that it could stay closely aligned.
But that was not to be.
Johnson, the face of the 2016 Brexit campaign, asserted that, since 52% had voted to "take back control" from the EU, he was not interested in accepting the rules of either the single market or the customs union.
The EU did not want to give unfettered privileges to a freewheeling, deregulated British economy outside the bloc, and so potentially encourage others to leave.
The result was a tortuous negotiation on a level playing field in competition - which the EU demanded in return for access to its market.
At one point, EU chief negotiator Michel Barnier even posted a picture of himself in London, staring at a sports field.
If there is to be a deal, it will cover goods but not the financial services that make London the only financial capital to rival New York. Services make up 80% of the British economy.
In essence, the agreement is a narrow free trade deal surrounded by other pacts on fisheries, transport, energy and cooperation in justice and policing.
Despite the agreement, goods trade will have more rules, more red tape and more cost. There will be some disruption at ports.
Everything from food safety regulation and exporting rules to product certification will change.
Britain's Office for Budget Responsibility says the economy will shrink by around 4 percent.
The UK, which imports about $107 billion more a year from the EU than it exports there, bickered until the end over fish - important for Britain's small fishing fleet but worth less than 0.1% of GDP.
Access to the EU market for London-based banks, insurers and asset managers is being handled outside the deal and will, from January 1, be patchy at best.