FOR years they have marched, en masse, against the powers in Madrid. Now, instead, their anger is aimed at those in Barcelona. Catalonia’s grassroots independentistes took to the streets last weekend for their annual national day protest, La Diada.

At least 150,000, according to local police, turned out. Many, it seems, did so to vent against their own political leaders, not their unionist opponents.

On the eve of the big day, Catalonia’s, pro-independence centre-left president Pere Aragonès faced cries of “traitor” from more radical campaigners. He was, at least one protestor was heard to say, a “lickspittle” of Pedro Sánchez, Spain’s socialist and, of course, unionist premier. Mr Aragonès did not go on the big march. Who can blame him?

Catalan nationalism, fatigued and frustrated, is turning on itself. Or at least that is the story being told in Barcelona.

This is, I think, a significant development. And not just for the north-east corner of Iberia, but for the northern third of Britain too.

Why? Because there are British unionists who hope Scotland’s independence movement, like Catalonia’s, will start to fray in the face of a muscular Spanish-style Naw to a new referendum.

The theory? That saying either “no, never” or even “not now” to indyref2 will pile pressure on mainstream Scottish nationalism. Moderates, the story goes, will get bored, hotter heads will go full off-putting Braveheart or turn on their own. Crudely, the idea is that yoons have to stand firm and wait for nats to wipe each other out.

Scotland, of course, is not Catalonia and Britain is not Spain. But there are, nevertheless, stories, ideas, trends which echo, bounce, vibe between one place and the other. Such as the notion that separatism, as world wire agencies call it, self-destructs without a democratic outlet.

So what is causing the Diada rancour? Political impasse.

This day – marking the fall of Barcelona to the Bourbons on September 11, 1714 – has morphed in to the independence movement’s big feel-good show of force, of solidarity, of defiance. The Assemblea Nacional Catalana or ANC is the grassroots organisation behind street action. This year its new leaders have been so unhappy with the pro-independence parties, such as Mr Aragonès’s Esquerra Republicana de Catalunya or ERC, that they have mooted running their own candidates against them.

Context, as ever, matters.

It is five years since local authorities tried, without any agreement from Madrid, to hold a referendum on breaking away from Spain. That unauthorized plebiscite, of course, ended with police hitting voters, shutting polling stations and rounding up organisers. Chunks of Catalonia’s political leadership were either jailed or forced into exile. This was, I suppose, muscular unionism, Castillian-style.

The crackdown was defining. It has shaped all the politics, and all the anti-politics, which has followed.

Last year independentistes kept their hold on power in Catalonia. Mr Aragonès became president of what he and his allies see as a nation and what some of his fiercest opponents think is a region. His ERC depends on coalition partners Junts.

The Catalan government, the Generalitat, has had other things to think about, not least handling the legal aftermath of the 2017 vote and subsequent arrest of politicians. But critics, not just the ANC, but Junts too, think the government’s progress is too slow.

Such grumbling came as support for independence hit a low of little more than 40% this summer.

Arguably worse, Catalans are simply losing interest. There is, after all, a lot else going on in the world.

Daniel Cetrà, a political scientist at the University of Barcelona, urges caution over polls showing barely two out of five Catalans know who is president of the Generalitat. But a block on progress to an independence referendum, he stressed, is having an impact. “Catalans are experiencing political fatigue and disengagement,” he said, “It is a country a bit tired of itself.”

Mr Cetrà divides Catalan nationalists in to two camps. The first is made up of pragmatists prepared for a long slog of negotiations with Madrid. The second are the 'impatients' who, perhaps like contestants in a TV singing competition, think they can secure independence just as long as they want it enough.

“The uncomfortable truth is that this may have become a ‘frozen’ conflict in which neither strategy works,” he said. “The socialist government in Madrid doesn’t have strong incentives to make ‘concessions’, not least with local and general elections coming up next year.

“And pro-independence ‘purists’ over-estimate their strength and fall into extreme forms of voluntarism: ‘If we’re not independent it’s because our leaders didn’t want it enough, or they betrayed the people by not implementing our democratic mandate’.”

Does this sound familiar? I think it does. As is so often said of Scotland, Catalonia is stuck. And that really does test nationalist mettle.

But it is not just nationalists who are at an impasse. So too are unionists. And this is as true of Scotland as it is of Catalonia.

Pro-Spain and pro-UK strategists will whistle along as Catalan nationalists fall out. But the “don’t let them vote” gambits in Iberia and Britain come with risks.

Neither the Spanish nor the British states seem to be looking for ways to re-image themselves as more pluri-national, more multi-polar polities capable of accommodating varied identities. Indeed, the chauvinistic, nationalistic right in both states is finding its voice. And an audience. Such muscular unionism – to repeat the maybe tediously overused term – was this week in The Times described as “imperialism” by the Scottish-born scholar Iain McLean. Me? I think it remains as big a threat to the states it purports to support as the ‘separatist’ nationalisms to which it responds.

Back in Barcelona historian Enric Ucelay-Da Cal this month told the AP agency that splits in the Catalan indy movement were a “hangover” adding: “you had the party and it didn’t work out.” But constitutional deadends are is not just a headache for independence supporters, in either Catalonia or Scotland.