There has been much excitement since the Queen’s Speech about the idea that the Scottish Parliament, with its separatist majority of Nationalist and Green MSPs, could ‘block Brexit’.

Below the hyperbole, this refers to the fact that the (formerly Great) Repeal Bill may require a ‘Legislative Consent Motion’ (LCM) from Holyrood.

As this primer in the explains, an LCM is a devise whereby a devolved legislature formally grants permission to Westminster to legislate on something which is usually a devolved matter. They’ve been used hundreds of times. But as the article explains, they are fundamentally a courtesy. Parliament is the sovereign entity at the heart of our constitution and it can legislate on any matter it wishes.

The Sewell Convention, on which LCMs are built, stipulates that Parliament will not ‘normally’ legislate on reserved issues. But that’s no basis for the idea of a block on Brexit: not only does the phrase ‘normal’ allow for extraordinary circumstances, which Brexit surely is, but it’s still just a convention – a powerful bit of soft pressure, but no more.

Once this is understood, we can get a more accurate view of the battlefield. This is not really a ‘constitutional crisis’: those tend to arise in systems where equally-matched arms of the constitution find themselves in a deadlock. Parliamentary sovereignty makes that almost impossible.

There are some enthusiasts for ‘federalism’ who hope that this foundation of our constitution might get re-written by the courts, and that briefing goes so far as to say that “there may even be grounds for a legal challenge”.

But we have only recently put this theory to the test, when the Scottish Government weighed into the Miller case over Article 50. Although the 11 justices split in their decision on the main case, they were united in rejecting the SNP’s attempt to conjure a devolved veto, and delivered a judgement which recognised that the Sewell Convention is inherently political and not legally enforceable.

Does this mean that an LCM, if required, wouldn’t be problematic? Not at all. The SNP may have continually failed to wring mileage out of constitutional grievances since the Brexit vote – a year ago today, as it happens – but that’s not something a responsible Government will want to put too often to the test.

But any ‘crisis’ will be political, not constitutional, and we can already see the outlines of a political solution taking shape. Ian Duncan, the new appointee to the Scottish Office, has talked in strong terms about the need to consult the Scottish Government, and the SNP are talking up how unacceptable it would be if powers over devolved policy areas repatriated from Brussels ended up exercised by London.

A deal whereby the Government agrees to pass all powers over devolved areas straight down to Holyrood, in exchange for an LCM, seems plausible at this point.

That’s not perfect: such powers have presumably been passed to the EU precisely because it was felt they could be better exercised by a higher, coordinating body. If you’re a Europhile who believed in the wisdom of such transfers ,then London ought to be the next best thing after Brussels, if not for all those laws then at least for some of them.

The demand that every power be passed straight to the devolved legislatures is a call to prioritise the nationalist aversion to London over the interests of good government and, by forcing the Government to buy off Nicola Sturgeon and Carwyn Jones, an LCM requirement will probably leave us with a somewhat less optimal distribution of powers within the UK post-Brexit.

But it can’t prevent Brexit from happening, at least constitutionally. The Government will have to negotiate the political waters with care.