Brussels - Next week's EU summit has been billed as a last chance to negotiate an orderly Brexit, but is the cliff edge really that close? When is the true deadline?
Officials from both London and Brussels say the draft of a Brexit deal must be reached by the summit dinner on October 17 -- or at the very most by mid November.
This is supposed to give Prime Minister Theresa May time to get a text approved by the British parliament in time for the March 29 divorce deadline.
But some European officials hint privately that the dates are not immoveable and all the recent urgency unnecessary. Can EU leaders kick the can down the road?
- Brussels deadline -
For Europe, the March deadline is purely technical, based on a never-used Article 50 process that dictates the timeline of a divorce from the EU.
Under Article 50 of the EU treaties, the two sides have two years to negotiate a divorce agreement.
Britain launched that process on March 29, 2017, so -- as far as European officials are concerned -- the deadline is that same date two years later.
But Britain's withdrawal deal will require ratification by the European Parliament.
Timeline of the Brexit talks
MEPs, led by their Brexit coordinator liberal leader Guy Verhofstadt, will make a lot of noise.
But few believe parliament will slow down or even block a landmark deal forged in fire by the 28 EU leaders.
In fact, insiders say the European Parliament could vote immediately before the March 30 cliff edge.
"Parliament could vote on a withdrawal agreement up until about March 25 or 26, assuming that the March 29 Brexit date holds," a parliamentary source said.
- London deadline -
"It would certainly not be desirable for the decision to be taken so tight up to the deadline, but ... it is technically possible," the source added.
The last session of the European Parliament is on April 18 before it breaks up for EU elections in late May.
So -- even if Brexit negotiations veer off course -- the Article 50 deadline can not be extended far.
British officials chafe at any casual attitude to the deadline.
"People need to realise that this vote may be the most important of our lifetime. That it's just not going to be fudged and rushed through," one said.
Indeed, British negotiators say Brexit talks with EU officials can continue into mid-November and no further.
That is because, if May is to avoid a no-deal catastrophe, she will need to provide as much time as possible for lawmakers to debate and approve the divorce.
A Brexit deal in October already leaves the "extremely compressed," wrote the Institute for Government, a Britain think tank.
If negotiations slip behind, passing the legislation in time will be a "heroic" task, it warned.
The EU withdrawal will be a landmark vote for Britain and experts cite previous major EU treaties passed by the UK parliament as a benchmark for the time needed.
The EU treaties of Rome and Maastricht each took around 40 sitting days to go through both the House of Commons and the House of Lords.
Before Brexit day there are about 70 sitting days between a theoretical deal mid-November, and around 50 from the already scheduled EU summit in December.
By Alex Pigman with Alice Ritchie in London