Famously, the United Kingdom is one of only three countries without a codified constitution, the others being Israel and New Zealand.

But the UK does have constitutional documents, a hotchpotch of statutes, precedents and conventions, which is what will concern the Supreme Court as of today. That it will meet in full and for most of this week underlines the unusual nature of what’s in play.

In extraordinary political times it might not seem so extraordinary, but we’re now as close to a constitutional crisis, or rather the makings of one, as the UK’s been since 1936, although the abdication looks like a walk in the park compared with Brexit.

Read more: Scots more worried about Brexit than rest of UK, study finds

And while the Supreme Court is supposed to fulfil a strictly constitutional role, its deliberations this week (and decision next month) cannot avoid being political.

As well as the central question of the Royal Prerogative and its (potential) use in triggering Article 50, before the 11 Justices will be submissions from the Scottish and Welsh governments, as well as some members of the Northern Ireland Assembly, something that highlights the increasingly quasi-federal nature of the UK.

The Lord Advocate’s submission wisely avoided talk of vetoes and focused instead on legislative consent, although it seems unlikely that’ll detain the Supreme Court for very long; the weasel word “normally” will let the UK Government off the hook. As a result, objections to the UK Government’s counterblast have rested, rather flimsily, upon its “tone” rather than anything more concrete.

Even so, the outcome could be a win-win for the Scottish Government. If the Justices agree that Scottish approval to trigger Article 50 is necessary, then all to the good, but even if they do not the SNP will be able to turn the snub to its advantage. The same was true of the Chancellor’s recent visit to Edinburgh, which produced helpful headlines about unreasonable Tories resisting reasonable Scottish demands.

Spreadsheet Phil’s use of the phrase “clutching at straws” might not have been diplomatic, but it was an accurate description of the Scottish Government’s approach so far. It’s still not clear what form this – due in the “next few weeks” for several weeks now – will actually take: a speech? A document? But then the truth is that ministers at Holyrood probably don’t know themselves.

It’s also become clear that there’s not really a distinct Scottish position when it comes to Brexit. Access to the single market and the need for migrant labour are issues across the whole of the UK, so when you drill down the only real Scottish dimension is what the devolution settlement looks like once the UK leaves the EU.

And although the SNP continues to argue that we’re hurtling towards a hard Brexit, that isn’t the mood music emanating from Westminster, where both David Davis and Boris Johnson have talked about the UK paying into the EU budget in order to get preferential access, a concession that generated surprisingly little dissent from the usual suspects.

Read more: Scots more worried about Brexit than rest of UK, study finds

So given the First Minister’s downgrading of her “red line” from continuing EU membership to membership of the single market, such an outcome would put her in a difficult position. Sure, she could try rallying the troops on the basis that “access” to the Single Market isn’t the same as “membership”, but that seems unlikely to be a runner. All roads lead to some sort of bespoke deal that probably won’t feel much different from the status quo.

Meanwhile, the SNP’s stance on two constitutional principles, the concept of parliamentary sovereignty versus that of “the people”, is typically confused. Having long rejected the former – as did the Unionist Lord Cooper in his famous 1953 opinion – they now opportunistically embrace it, while Nationalists are doing a good job of resisting two examples of the latter, not only the 2014 independence referendum (in which the majority self-determined in favour of the Union) and June’s EU ballot (in which a majority of the UK electorate opted to Leave).

Nationalists, of course, behave as if Westminster has no right to decide anything concerning Scotland, as if it were already independent, but the 1998 Scotland Act (which the SNP accepted and supported) makes clear that the constitution – which surely covers Brexit – remains a reserved matter, although that and subsequent events have transformed the old unitary British constitution into something much more nuanced.

Last week in Dublin Ms Sturgeon repeated her tenuous argument that while England and Wales had a democratic right to leave the EU, she doesn’t accept any “mandate” exists to exit the single market. The SNP leader also devoted some of her weekend National Council speech to attacking Scottish Tory leader Ruth Davidson for changing “tack” on the single market, but that might be because her side lost the referendum, something Conservatives appear to find easier to accept than Nationalists.

In response to Philip Hammond’s comments the First Minister also accused him of “arrogance” for doing no more than restating his government’s position about the unlikelihood of a differentiated Scottish deal. But then arrogance is not confined to Tories or Westminster – is it not arrogant to string everyone along in a will she/won’t she charade on a second independence referendum even although the dogs in the street know what the pre-ordained conclusion is?

Beyond fawning Irish senators, meanwhile, it’s increasingly clear the Scottish Government doesn’t even enjoy support from its devolved counterparts. At the most recent British-Irish Council meeting the feng shui didn’t seem to favour Mike Russell, with Welsh First Minister Carwyn Jones declaring beforehand that differentiated access to the single market couldn’t “possibly work”, a helpful intervention from the UK Government’s point of view.

Read more: Scots more worried about Brexit than rest of UK, study finds

Then there’s trouble on the home front. In several recent speeches the First Minister has acknowledged a key group of voters, those who wanted independence from both the UK and the EU, saying she understands their “desire for change”. Previously, the SNP believed these voters were still likely to vote Yes if asked to do so, although recent polling actually shows diminishing enthusiasm.

That, combined with the likely outcome of the EU negotiations, does not really add up to a second independence referendum any time soon. Brexit certainly makes the Unionist case politically harder but also economically easier, in that it highlights the size of the UK single market vis-à-vis the EU, something to which the SNP still lacks a coherent response beyond maintaining the fiction that the latter is more important to Scotland than the former.

If, meanwhile, the Supreme Court decides after this week that an Act of Parliament is necessary then the UK Government is clearly prepared to introduce a short bill, the sort of muddling through that an unwritten constitution inevitably produces. But far from this “constitutional crisis” being an “extremely good thing” from a Nationalist point of view, as Alex Salmond claimed yesterday, equally it could turn out to be a damp squib.