THIS jelly needs nailed. But like the real thing, it’s a tricky manoeuvre to get a grip on the jiggling object and to wield your mallet at the same time. So bear with me. This is Brexit litigation week. As anyone who tuned into the Supreme Court knows only too well, the legal niceties of the case take no prisoners. The amateur and interested viewer were left largely uncatered for by the two days of legal fencing between the seven justices and the advocates pressing their respective cases. But let’s try to break it down.

At its most simple, the litigation is about Holyrood’s EU Continuity Bill. The UK Government says the Bill is outside of Holyrood’s powers under the Scotland Act. They insist that Westminster’s Brexit legislation – passed by the Lords and Commons in the teeth of MSPs' objections – should apply instead. They want to give the whole nation – which is to say, UK ministers – a single rulebook for ripping up EU law after exit day, across the whole frontier of devolved and reserved issues.

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The Lord Advocate, by contrast, argues that the Scottish Parliament was well within its rights to lay the groundwork for dealing with devolved EU law back in March. The Bill must stand. In this argument, he is supported by the law officers from Wales and Northern Ireland, both of whom express concerns that the central government is – yet again – treating the UK constitution like a historical re-enactment society, with scant regard to the modern reality of devolved governance.

Because the cynicism – or you might say, the cunning, depending on your point of view – exhibited by the UK Government’s legal case really is something else. And the character prosecuting this constitutional horror show – Theresa May’s Advocate General, Richard Keen – is perfect casting in the role.

The owner of a small castle and a minor firearms conviction – Keen is the distilled essence of all of the worst features of the Edinburgh legal establishment. With the demeanour of a constipated goshawk and an ego giving the same altitude reading as Kilimanjaro, Baron Keen of Elie was fashioned by nature to be the condescending voice of organised privilege and constitutional reaction. And don’t underestimate him. He’s good at it. Clever, clever. Maybe too clever.

So what was his argument?

To explain his logic – let’s start with a metaphor from the private housing market, a traffic dear to every Tory’s heart. You put your house and home up for sale. A buyer likes the cut of your dado rail and makes you an offer. You accept. Deal done?

So you might think. But along waddles your Gazumper. A wealthy customer, the Gazumper doesn’t believe in old-fashioned concepts like first dibs and a word being your bond. The deal to sell, from the Gazumper’s perspective, is just a temporary setback for the enterprising home owner with cash in hand and the will to win.

The Gazumper flourishes a fist full of notes at the seller, tempting them to break their earlier accord. Wouldn’t you rather sell your home to me, than the cutpurse who offered you so much less? It takes a soul of a certain fortitude not to screw over the first buyer in exchange for bigger bucks. And so you’re gazumped. The second body to streak across the finish line carries off the gold. Or in this case, the terraced two-bed with misjudged avocado bathroom suite.

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The gazumping metaphor can be stretched – a little inexactly – across the contours of Baron Keen’s Brexit case. Yes, he concedes, Holyrood did indeed pass its EU Continuity Bill during the spring. Yes indeed, the Scottish Government proposals won the support of an overwhelming majority of MSPs. He is also gracefully prepared to allow that Westminster didn’t get its Act together till three months later, passing its parallel Brexit Bill and passing it on to Liz Windsor to affix her John Hancock. Oyez, oyez, oyez.

But like our keen-eyed Gazumper, Lord Keen wants to argue the later UK legislation trumps the earlier efforts of the Scottish Parliament.

And here’s how he does so. When Theresa May’s law officers referred the Scottish Brexit Bill to the Supreme Court, a Bill’s status is frozen. The final proposals don’t receive royal assent. They aren’t law. The Bill is left thumbing through elderly copies of Vogue in the waiting room, till the Supreme Court decides whether or not it falls within Holyrood’s legislative competence.

Against that backdrop, with a squint and a little imagination, Lord Keen maintains that because Westminster’s legislation hit the statute book first, Holyrood’s earlier plans should be regarded as a scandalous attempt to “frustrate” the will of the UK’s “sovereign Parliament”. Even though – you know – that will didn’t coalesce into a final form until 92 days after MSPs took the final vote on the Scottish proposals. Baron Keen is clearly dual-qualified in Gallifrey.

To put it even more simply: on the UK Government’s own evidence, it used the Scotland Act to exercise a pocket veto over a Holyrood Bill it doesn’t like, and now relies on that veto to win its case. The parliamentary authorities in Edinburgh will have to update their standard equipment for new MSPs – now to include 10 red biros, one elderly Windows computer per staffer, and a slightly cracked crystal ball, with one incautious owner, for predicting the future.

The Lord Advocate’s riposte to Richard Keen’s timewarp jurisprudence was simple, logical, and consistent with a linear time frame. “The Scottish Bill was passed many months ago – it was not intended to modify the UK Bill and could not do so,” he said.

But there are more fundamental issues about the Tardis chicanery implicit in the UK Government’s position. The professor of public law at the University of Strathclyde posed a good question. “Should law officers be making Supreme Court references on spurious grounds so as to secure a tactical delay to enactment that guarantees them victory?” Aileen McHarg wondered.

I imagine Baron Keen might respond: all’s fair in love, war and Brexit. You’ve been gazumped. Behold my towering intellect. Marvel at the efficiency of my cynicism.

Personally, I’m not sure I care to hear the concept of devolution addressed in these terms. There’s an ugly relish to Richard Keen’s submissions about how meaningless devolution remains in his understanding of the British constitution. Fundamentally, it is Unionists and devolutionists of a more considered stripe who ought to be most alarmed by his arguments.

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They’re the ones who insist this edifice can be rebuilt to reflect contemporary understandings of what Britain is. They’re the ones who insist the UK’s famously mobile constitution can bend its shape to accommodate new ideas and federated structures. Not so.

This fantasy constitution building is bust. Jacob Rees-Mogg will be planted in the family crypt in a pinstriped winding sheet long before the UK contemplates any departure from the mantra that “power devolved is power retained”. The cargo cult of a sovereign Westminster has, if anything, been more powerfully reinforced by Brexit.

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Baron Keen of Elie is just its latest mouthpiece, the Supreme Court its latest setting. And to this extent, the Advocate General has done us all a service. He put the central point with brutal clarity. Constitutionally, devolution exists on sufferance. For Britain, there will be no reformation and no reform.