Where next for the UK's Brexit negotiations?
What are the next phases in the cumbersome process for this country of leaving the EU?
What can and must be agreed between the UK and the EU by the autumn of 2018 - which is the target date for the EU-wide parliamentary approvals process to begin?
The first important milestone should be passed on Thursday, when EU leaders are set to authorise the agreement between Theresa May and the European Commission on the divorce bill, the methodology for keeping open the border between Northern Ireland and the Republic, and the rights of EU Migrants.
If all goes to plan, EU government heads will also agree guidelines for the Commission negotiators on the nature of the two year transition Britain wants from formal exit on 29 March 2019 to full severance of the umbilical cord.
That guidance will then be turned into a detailed negotiating mandate or directive to be agreed by another government heads summit or council at the end of January.
The contentious issues are:
1) Will the UK be allowed to negotiate trade deals with third party countries during the transition?
2) Will the UK be able to setup a scheme to register new EU migrants to the UK who arrive after March 2019?
3) Will the UK have to adopt the changing EU legislation and court decisions during the two years of transition?
4) Can Michael Gove have his wish granted that we will leave the Common Fisheries Policy at the end of March 2019 rather than after transition?
From discussions with officials here and in Brussels, my view is that:
1) Trade negotiations with third party countries will probably be permitted, though no free-trade-deal could be formally agreed till after transition (so Liam Fox keeps his job!);
2) Registration of EU migrants will be permitted, because it happens in other EU countries already;
3) The EU will insist we adopt new EU laws during the transition (which ardent Brexiteers will hate);
4) There is no chance of the UK being able to leave the Common Fisheries Policy until after transition (my sense is that Gove has already recognised that).
All that could be settled by March - which would reassure multinational companies that they don't need to press the relocate button and shift massive amounts of investment and people outside the UK (or at least not quite yet).
But what about the all-important question of our long term trading relationship with the world's biggest market, the EU's internal market?
Well there is no chance of talks on a future trade deal with the EU starting in any meaningful form until April, I am reliably told by EU officials.
But the really important thing about those initial EU trade talks is they won't be detailed or administrative, only political.
The reason is that under EU rules, the legally enforceable elements of a future trade deal cannot be negotiated till after Brexit, or after March 2019.
So the plan is for the negotiations in 2018 to be exclusively about the political parameters of our future trade relationship with the EU.
This will need prior decisions by May and her cabinet abut whether we want completely tariff free trade with the EU, what kind of regulatory convergence we will accept with the EU, and whether there is a way of minimising customs checks.
All that is big politics and contentious, especially in the Conservative Party.
And as I have mentioned before, the PM has not yet had the guts to endure any kind of cabinet discussion about what kind of trading future with the EU her ministers see for the UK, because they are divided on the central question of how far the UK should follow EU rules and regulations in perpetuity.
Wish May luck, because that first Cabinet conversation will happen next week.
If the PM can reach a common position on all this with her cabinet, and then a common position with the rest of the EU, there will be a short document of perhaps 30 pages agreed by October of 2018.
And that political document would be turned into a formal trade deal during the transition after the UK leaves in the spring of 2019.
Quite how long and complicated those proper and formal trade negotiations turn out to be will depend on whether the UK has asked for something simple, like zero tariffs in all cases, and limited to manufacturing, or a more complex set of duties and access agreements, representing the gamut of UK industries, including services.
If the UK wants something relatively modest, that could be approved just by the EU Council and Commission. We would be properly out of the EU, and pretty disconnected from it, by the end of 2020 or so.
Anything more ambitious - a deep and intimate trading relationship between our entire economy and theirs, plus formalised co-operation on security, and the fight against crime and terrorism including some kind of continued membership of Europol - it harder.
Such a deal would take much longer both to nail down and specify, and then to agree, because it would have to be approved by relevant parliaments in all member countries.
A big judgement that May and her colleagues have to make, on behalf of all of us, is whether to go for a quick and dirty departure from the EU, with a future relationship that is shallow and limited, or aim for a deeper, richer long-term partnership with the EU - which may take many years to finalise.
If we know where we're heading, is speed of the essence?