THERESA May’s speech to the Scottish Conservative conference has dominated events at Holyrood this week. No, not the one she was meant to give in Aberdeen before the snow intervened. The one she gave exactly a year ago in Glasgow.

You can trace a line from its tin-eared presumptuousness directly to the SNP’s Brexit continuity Bill. The Brexit referendum unlocked a constitutional Pandora’s box; Mrs May’s speech raised the lid.

In it, and this still gets a laugh, the PM declared: “No one can doubt our party’s credentials on devolution.” She then burnished those credentials by casually setting fire to the devolution settlement.

After all, it had been “designed in 1998 without any thought of a potential Brexit”. To protect the UK internal market, her government would “ensure that the right powers sit at the right level”. For too long, the attitude in Whitehall had been to “devolve and forget”, she said. No more. The UK Government was going to “unashamedly assert” its duty to act for the whole UK.

Translation: devolved powers repatriated from Brussels at Brexit won’t be devolved by default, as per that musty, old outdated devolution settlement. Westminster is going to intercept and hoard them instead in a bolder, brighter new devolution settlement, albeit crudely imposed.

Immediately, the Scottish and Welsh governments denounced it as a “power grab” and still do. Soon afterwards, the EU Withdrawal Bill (EUWB) fleshed out the plan.

Clause 11 said the 1998 Scotland Act, the founding text of devolution, would be amended to ensure no devolved power returning from Europe reached Holyrood unless the UK government decreed it. Instead of being devolved by default, they would be reserved by default, an inversion of the existing settlement.

The intention was to hold them pending the creation of UK-wide common frameworks in areas such as agriculture and food-labelling, to avoid a fractured internal market.

The fear was that the devolved legislatures would, for perverse reasons unknown, pass their own quirky regulations in these areas, turning the UK into a patchwork of red tape, disrupting internal trade and deterring overseas business.

Clause 11 has been rejected by every party at Holyrood, including the Tories, as something which would undermine devolution.

So in recent weeks, the UK government has changed its tune. Now, it only wants 25 of the 111 devolved competencies involved to go to Westminster, and the “vast majority” can go to Holyrood.

This is a big shift, but also underscores how badly wrong the EUWB got it on devolution, and what a mistake that speech was.

Cabinet Office minister David Lidington this week said he expected common frameworks would be settled by “consensus and agreement”. But there was a huge caveat. Or what he called an “an important protection”.

If Edinburgh and London can’t agree “the UK parliament could protect the essential interests of business and consumers in every part of the Kingdom”. In other words, agreements are nice but not essential. The UK reserves the right to legislate where it sees fit.

The SNP Government isn’t buying. It wants all the powers devolved, or at very least common frameworks settled by genuine agreement, not token consultation.

Hence the Brexit continuity bill, which aims to transfer relevant EU law into Scots law if the stalemate continues, Holyrood withholds legislative consent for the EUWB, and we all go deeper down the constitutional rabbit hole.

If the UK amends the EUWB to Holyrood’s satisfaction, the continuity bill will be dropped. But Nicola Sturgeon said this week a clash seemed “very likely”. At FMQs, she said it was “not a situation in which we have our positions and can meet in the middle in some vague way. It is a fundamental issue of principle. Consultation is not enough; the consent of the Scottish Parliament should be required.”

Many at Holyrood liken the EUWB fight to the one over the “fiscal framework” and Holyrood’s new tax powers. After months of stalled haggling, George Osborne made the problem disappear by throwing millions at John Swinney. Governments can always find extra money to grease a deal if they must.

The EUWB fight feels different. Money alone won’t end it. The UK might offer cash, but the FM could never be seen to put English gold ahead of a fundamental principle.

It’s not just about principle, of course. It’s about raw power. The SNP complain that Clause 11 would hand Westminster a veto over what Holyrood could do. But the SNP’s solution gives Holyrood a veto.

If common frameworks could only be created by agreement, Holyrood could keep large swathes of policy frozen in their pre-Brexit state by withholding consent.

Or ministers could use talks on frameworks to extract more money and powers from Westminster. The political term is leverage, but most people call it blackmail.

So giving Holyrood a brake on Brexit is deeply unattractive from the UK’s perspective. The idea of the sovereign parliament being blocked by a subordinate one after “taking back control” would also see Brexiter MPs in revolt.

Common sense points to a deal. The continuity Bill is high risk for Edinburgh and London, and Holyrood passing it could start an unpredictable chain of events.

Ms Sturgeon says a deal on the EUWB is still her preference. But don’t bet on it happening. A year on from that toxic conference speech, both sides are dug into positions they will find very hard to give up.