Under normal circumstances, UK Prime Ministers do not go dashing off to Brussels at a drop of a hat to have dinner with the Commission President. And in days of yore, it would never happened at all. Can you imagine Thatcher "leaving on a jet plane" to see Delors all in a rush? She would have summoned him to London and expected him to turn up.
Thatcher notwithstanding, given that Mrs May has done the unspeakable, we may safely assume that these are not normal circumstances, especially in the light of the post-dinner statement
which, to say the very least, lacks transparency.
In fact, the whole thing is more than a bit bizarre. After all the drama, it seems, they had a "constructive exchange on current European and global challenges", including discussing "their common interest in preserving the Iran nuclear deal and their work on strengthening the security of citizens in Europe, notably on the fight against terrorism".
I really have trouble believing, though, that Mrs May went to the trouble of making an unscheduled stop in Brussels, then to talk about the Iran nuclear deal and "strengthening the security of citizens in Europe".
Nor, in respect of the Article 50 negotiations, does it seem credible that Mrs May and President Juncker "agreed that these issues are discussed in the framework agreed between the EU27 and the United Kingdom, as set out in Article 50 of the Treaty on European Union". Mrs May really didn't go all the way to Brussels to find that out.
That left the pair to review the progress made in the Article 50 negotiations so far, leading to what appears to be the only substantive agreement, that "these efforts should accelerate over the months to come".
Even if that's all there is on offer, I suppose we should be vaguely comforted by the final observation in the joint statement, which told us that the working dinner, which apparently only lasted two hours, "took place in a constructive and friendly atmosphere".
However, one has to note that no one is claiming that the talks themselves were "constructive and friendly", and I would not be the first to have had a blazing row in a location famed for its friendly atmosphere. In this case, the text allows for the tensions to be very close to the surface.
What would have been concentrating minds, though, is that today is the meeting of the General Affairs Council in Luxembourg. This is the body comprising Member State foreign ministers which traditionally settles the agendas for the European Council meetings.
In this case, it is the Friday meet of the European Council, meeting as 27, which is going to decide on the next moves for the Brexit negotiations, so it would have been vital to have set the tone for the General Affairs Council if there was any chance of influencing matters.
That said, although we have seen frenetic activity on the part of Mrs May, having placed calls with Angela Merkel, French president, Emmanuel Macron, and the Irish taoiseach, Leo Varadkar, there are no indications that sentiment is moving in the direction of the UK government.
In this context, EU "diplomats" are widely cited, reiterating the same point we've been hearing endlessly from Barnier, that the UK has not made "sufficient progress" to allow the talks to move on.
This, in itself, makes one wonder why the Prime Minister was deployed in Brussels. Looking at the move in chess terms, it is the equivalent of bringing the queen into play – something which one often reserves until she can have decisive effect. Certainly, one does not risk the queen for a pawn – which is rather what seems to have been done here.
In those terms, the "queen" seems to have been played without measurable effect – which opens Mrs May up to ridicule and even humiliation if this eleventh-hour intervention is seen to have achieved nothing of consequence. And, once she has intervened, the cupboard is bare. There is nothing else to bring into play.
It is possible, though, that there might have been another agenda being worked. It might be that Mrs May is keen to face Juncker – and Michel Barnier, who was also at the dinner, alongside his opposite number, David Davis – in order to convey to them personally that there are no further concessions on offer, so there is no point manoeuvring for more.
This would be a direct way of saying that, if agreement can't be reached in October, then holding over to December is not going to get the "colleagues" a better deal. The message might have been "settle now" or face the prospect of the talks collapsing later.
Nevertheless, with nothing further to go on, the real reasons for this meeting, and the actual outcome, will remain obscure – for a short while at least. The first clue that anything has been achieved might come from today's General Affairs Council, but it may also spell the end for Mrs May's ambitions.
Her high risk strategy could, therefore, have another objective. Her willingness to go to Brussels and put the UK case directly to Juncker might be part of the wider attempt to demonstrate that she has gone the extra mile, positioning the Commission as being responsible for the blockage. Played out to a domestic audience, this would be used to legitimise a walk-out later in the talks.
One way or another, we might know a little more by the end of the day, but it will take until Friday before we're fully appraised of the situation. I'm still not prepared to rule out the possibility that Mrs May is planning a high-profile walk-out, perhaps in response to the Friday Council, in which case this dinner will most certainly have been a preparatory step.