On Thursday, Theresa May travels to Brussels to meet with the remaining 27 EU leaders, where she is expected to request an extension to Article 50 , the legal process by which Britain is leaving the EU. If the EU27 agree, as they probably will, Brexit will be delayed beyond the current deadline of March 29. Leaving aside the gravity of this epic failure of British Brexit policy, the key question is how long will the delay last?

There are two likely options. The first is a short delay, which Downing Street said on Wednesday it would request . This would give the UK government a little more time to get its Withdrawal Agreement through Parliament, perhaps sweetened with some changes to the accompanying political declaration.

Or, the EU could offer May a much longer extension, possibly lasting years, to give to the UK more breathing space in which to untangle its Brexit mess. The EU says it would only grant a longer delay if there was a good reason for doing so.

Less likely -- but not impossible -- is that the EU refuses a delay altogether. European diplomatic sources have been clear over the past few months that any kind of extension would be far easier to swallow if the UK made clear its long-term intentions, rather than putting things off for no reason. To put it mildly, clarity has hitherto not been Britain's strong point.

Any Brexit delay requires the unanimous approval of the European Council, the EU's supreme decision-making body that includes the leaders of each member state, meeting in Brussels this week. This is where difficulties begin. Since the start of the whole process, Brexiteers have boldly asserted that the unity of the EU27 would eventually crack and the UK could finally get its way.

It didn't. To date, the EU has stood firmly by the deal it reached with the UK -- the so-called Withdrawal Agreement -- insisting it was locked down and ready for Britain to approve.

But given the UK Parliament's reluctance to do so, and the consequent prospect of a delay to Brexit, something interesting has happened. For the first time in the Brexit process, we are approaching a European Council summit where the behavior of the EU can't easily be predicted.

The difficulty for the EU is that, long or short, any delay comes with complications. And this is where opinions in European capitals start to diverge.

If the UK hasn't left the EU by May 22, it might have to take part in elections to the European Parliamentary elections, which begin the following day. Not doing so could be a breach of the UK's obligations as a member state.

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And if that happens, there is a real concern in Brussels that hardline Euroskeptics could stand for election, in protest at Britain not yet having yet Brexited. They might find a receptive public, and in turn, join interesting new friends in the European Parliament. Sound far fetched? An EU source recently told CNN of worries in Brussels that far-right figures like Tommy Robinson could end up as Members of the European Parliament, with all the associated attention that brings.

So a short delay is the preferred option of many in Brussels, especially in the Parliament. But that brings its own set of issues. First, there is no guarantee that by the end of it, the UK Parliament would have given a thumbs up to May's deal. In reality, it could just mean a delay to a no-deal Brexit that almost everyone claims they want to avoid, but still remains the default legal position.

The EU's preference is that Britain ratifies the Withdrawal Agreement. This is where the prospect of a lengthy delay plays into the thinking of some.

A long delay presents the UK, potentially, with a choice. If it is to take part in the European elections, then it must legislate to do so before April 11. In that scenario, the EU could propose a longish delay of around two years, with a fixed end point, but with a neat get-out clause. Were the House of Commons to approve May's Brexit deal within that period, the UK would flip out of the EU and the Article 50 extension would be reincarnated as the two-year transition, as per the current Withdrawal Agreement.

If that all sounds a little fiddly, here it is in simpler language. UK lawmakers would be presented with a choice of voting to leave the EU with a deal that they may not love, or remain as a full member state and what that leads to is anyone's guess: A general election, another referendum -- take your pick of undesirable outcomes.

All of this was complicated further on Monday, when the Speaker of the House of Commons lobbed in a constitutional hand grenade. John Bercow pronounced that Theresa May could not bring her Brexit deal back for a new vote in Parliament without the question being asked sufficiently differently from the one defeated last week.

While his statement has been interpreted differently by virtually everyone, it seems clear that if the EU gives May something substantial -- such as a new Brexit timetable -- that would be enough to justify a third vote in Parliament.

That puts the ball to some extent in the EU's court, even if no one has a real idea of what they are likely to do with it.

Any delay to Brexit would of course be a humiliation for the UK, politically. But it would have the effect of keeping May's deal alive for now, and allow her to whack her rebel MPs around the head with the threat of an extended stay in the EU if they don't fall into line.

If all of this sounds like confusing and opaque, that's because it is. And if it sounds irresponsible and risky, please be reminded that as things stand, Brexit happens in 10 days.

Finally, don't forget that this is just act one. If the Withdrawal Agreement is eventually approved, or if Britain tumbles out of the EU without an agreement being reached, what comes next promises to be even more intractable and more bitterly fought than anything we've seen so far. As one well-placed EU source said of the Brexit talks to date: "This was supposed to be the easy bit."