Media playback is unsupported on your device Media caption Will Catalonia say adios to Spain and become independent? Watch Paul Mason's full Newsnight report

If Catalonia does, one day, get its own air force, it will probably be able to afford something better than Spitfires.

For now the kit-built replica planes zoom acrobatically across the beach in Barcelona, the crowd's "oohs and ahhs" moderated by that essential Catalan characteristic: cool.

They shelter under umbrellas to avoid getting tanned. And they chat. And what they chat about is beginning to cause a quiet terror in Madrid, and in Brussels. Leaving Spain.

It's no longer about what people are feeling in their hearts, it's what they feel in their pockets too. And the feeling is that they would be a lot better off if they were not a part of Spain Eduard Castells, Barcelona resident

"My feeling is that the Spanish government has totally rejected what is happening here," says Jorge Fernandez, who has come here to watch the show. "They have spread rejection and hate with comments calling us 'the damn Catalans that don't want to collaborate'."

Another spectator, Eduard Castells, says: "The situation has evidently changed a lot. It's no longer about what people are feeling in their hearts, it's what they feel in their pockets too. And the feeling is that they would be a lot better off if they were not a part of Spain."

Three weeks ago one and a half million Catalans went on the streets, with outright demands for independence much higher in the mix than ever.

When the government in Madrid refused the region's demand for a new fiscal settlement, allowing it to keep more of the tax it raises, its government, led by the Convergence and Union (CiU) parties, called snap elections.

They want a referendum on Catalonia's future: through legal means or otherwise.

Oriol Pujol, the general secretary of Convergence, tells me: "We have an enormous fiscal transfer to Spain - about 8% or 9% of GDP - and never returns, year after year. And we could agree to carry on with that: there's no problem with agreeing to show solidarity with the rest of Spain. But when we have to make double cuts in services, when taxes are double - we have to make a change."

But he is keen to stress this is not just the result of the economic problems that have seen the region demand a 5bn euro bailout from Madrid:

"One cause of it is the crisis, but the crisis just gave the last push. It's the addition of obstacles, one on top of the other by Madrid, over the past two years. Political obstacles - and obstacles to identity, which really says to us there is no option to have Catalonia as we imagine it inside the Spanish state."

'Germany of Spain'

If, as expected the CiU wins the regional election on 25 November, then the clash over a referendum could crucially affect the course of the coming sovereign bailout for Spain.

If we exhaust all legal routes to get a referendum we won't stop Oriol Pujol, General secretary of Convergence party

"If we exhaust all legal routes to get a referendum we won't stop," says Mr Pujol.

I ask him, point blank if the region will call a referendum in defiance of the national courts and constitution.

"There will be no way to avoid it. If we don't deliver it someone else will. More radical parties. But in a negotiation," he smiles, "it's not the best thing to reveal what you are going to do next."

Bond markets, which have for 12 months tried to price the risk of a eurozone breakup, now have to calculate the possibility of the breakup of the Spanish state - for secession in Barcelona would surely prompt centrifugal tendencies in the Basque region, and exacerbate the fiscal crisis in the poorest regions.

Mr Pujol says that an independent Catalonia - often called the "Germany of Spain", for its high GDP and industrial base - could play a role in turning around the image north Europe has of southern Europe.

But the rise of Catalan nationalism is provoking tension in Spain itself. When I vox-popped villagers in neighbouring Valencia this week, about the impact of the crisis there, talk turned among the oldsters, who had lived through the Civil War, to "the Catalans" - the word is almost spat.

"It's outrageous!" one elderly lady smacked her fist into her palm. "We'll never let them leave!'

Last week a serving officer in the Spanish army, Colonel Francisco Aleman, upped the stakes, telling a website "Catalan independence? Over my dead body and that of many soldiers". Adding that the crisis was already "like 1936" - the year the Civil War began - "only without the blood".

Mr Pujol smiles painfully when I put this to him. It's not exactly laughable he says; it has to be taken seriously:

"There are no other options than democratic answers - knowing the whole EU and international community are observing what Spain answers. It's not the moment: we passed that some years ago."

"The politics of fear, not only the comment of this person from the army, will appear: we know that. But the process is so driven by enthusiasm that we think such comments show how weak Spain is faced with the process in Catalonia."

National sentiment

If they ever do become a country, they will of course have no trouble fielding a football team. At Barcelona fans' bar, the supporters watching their team trounce Benfica are adamant, the region will leave Spain:

"Two or three years ago people would tell you 'hey, that independence thing will never happen, don't get too excited about it and don't expect too much'. And now, after what has happened in the month and a half it is amazing."

Image copyright Getty Images Image caption The Catalan parliament recently voted for an independence referendum

"I feel Catalan," insists another. "My passport and ID card say I'm Spanish, but I just don't feel Spanish."

And here is the problem. You can dispute the economic costs of Catalan independence, but at least you can measure it with facts and figures. What you cannot measure is feeling: and there's a huge wave of national sentiment in Catalonia, sparked by the austerity, but drawing above all on anger at Madrid's perceived power grab.

"For the past 10 years Spain constructed its relationship with Catalonia on the separation of powers," Raul Ramos, an economics professor at Barcelona University, tells me"; "economic power in Barcelona, political power in Madrid. But now, to impose the bailout conditions, Madrid has to concentrate economic power in the centre. That's what's driven Catalan politicians to act."

Two years ago, when I put footage of a million strong Catalan demonstration into a report about the economic crisis, I had tweets back saying "the two aren't linked".

For years the threat of Catalan recession has been rhetorical; always producing a fiscal compromise with Madrid. But now Madrid has nothing left to offer.

Under Franco people died for the right to speak their own language, sing their own folk songs, dance the Sardana in the shade of the old cathedral. And in the years after, this cultural freedom has been enough to contain demands for independence.

But the crisis changes everything. And we still don't know where the crisis ends.