BARCELONA, Spain (Reuters) - The separatist flag of Catalonia - with its yellow and red stripes, blue triangle and white star - was a rare sight on the streets of Barcelona a decade ago. Now, it is almost ubiquitous.
Two thousand km to the north in Scotland, the blue-and-white saltire has always been popular. But that flag too increasingly symbolises something new, that after more than 400 years within the United Kingdom Scotland may be on the verge of demanding a divorce.
For all the focus on the risk of the euro zone falling apart, some suspect this decade may be better remembered as the time when two of Europe's most permanent states began to break apart.
Pro-independence parties in Scotland and Catalonia are preparing for referendums next year that they hope could see their regions secede for good - which some analysts suspect might encourage others in Europe to follow suit.
There are considerable differences between the two regions. Scotland has always been referred to as a separate "country" within the United Kingdom, while Catalonia's claims to self rule are rooted in the history of the Middle Ages.
Prime Minister David Cameron's government has agreed to co-operate with the autumn 2014 Scottish referendum, though it is campaigning vigorously against any split.
In contrast, Madrid has declared it will fight a Catalan referendum on constitutional grounds. The separatist parties that run the region are keen to push ahead anyway and match Scotland with a 2014 vote.
Some suspect the two campaigns will feed off each other in the months to come. Each cause is marshalling a similar range of emotional, practical and cold-blooded economic arguments as well as trading off widespread frustration with those in power in the traditional national capital.
Alfred Bosch, leader of the Republican Left, or ERC, bloc in Spanish parliament that has long lobbied for independence, said separatist politicians in Spain do keep an eye on what's happening in Scotland.
In both countries "there are the underlying emotional arguments for independence, then there are the more rational economic ones. What we are seeing is that they are coming together."
Polls vary, but at least one survey has suggested more than half of Catalonian voters would vote for a separate state if given the chance. That compares to figures of just over a third in Scotland - although those on both sides of the argument in that country say it is entirely possible numbers could change between now and the final vote.
Pro-independence activists in both countries are quick to stress they see themselves as part of a wider trend. The number of countries of the world has almost trebled since 1945 as African and Asian states broke free of colonial masters and with the fall of the Soviet Union creating a plethora of new nations across Eastern Europe and Central Asia.
In Brussels, Scottish and Catalan parties are already forging something of an alliance with Belgian Flemish parties.
"The global trend has been moving in this direction for some time," Fiona Hyslop, cabinet secretary for external affairs for the pro-independence Scottish government, told Reuters recently.
"Many countries which were not independent 20 years ago have gained their independence and are now full members of the European Union."
The modern contours of both Britain and Spain were drawn in the 15th and 16th centuries just as they began hundreds of years of imperial expansion that brought wealth and power.
Neither nation embarked on the kind of deliberate centrally coordinated efforts to build a national identity seen in newer nations such as Germany and Italy under Bismarck and Garibaldi respectively - or in France under Napoleon.
What may be giving fuel to the cause of separatism now is a growing sense of frustration and alienation from the powers-that-be in London, Madrid and many other capitals. The economic crisis, it seems, has made that even more pronounced.
"Whatever happens, these movements are going to have an impact. You're going to get more calls for devolution," said David Lea, Western Europe analyst at Control Risks.
"Part of it is obviously the crisis, but there are other factors as well: the rise of social media, much broader unhappiness with the status quo."
In Edinburgh, the rise of the Scottish National Party - now a majority government in the parliament - is seen more a result of their perceived administrative competence and a lack of enthusiasm for London-based parties than widespread pro-independence sentiment. The SNP hopes that is already changing as the referendum nears.
In Catalonia, one of the richest areas of Spain, there is widespread anger over what many see as too much money passing to the rest of the country. The Catalan independence movement has also proved increasingly effective at tapping into the wider sense of anger at government and big business produced by still-deepening economic woes.
"For me, it's something sentimental I got from my father," salesman Miquel Blas, 35, says of his attachment to the idea of Catalan independence. "But the real support for independence has come with the crisis."
Another Barcelona resident, real estate agent Maria Caralt, 40, says intertwining the two issues is unhealthy, however.
"People talk about independence and they talk about the crisis and they all get mixed together," she says. "But I still think independence is a good idea. It would be better and easier to manage a small country."
Not one of those who spoke to Reuters on the streets of Barcelona were enthusiastic about maintaining a unified state. Those who planned to vote against independence cited their cynicism about politicians in general and said they doubted that leaders of a separatist Catalonia would run it any better.
In London and Madrid, mainstream political parties opposed to independence are already beginning to work together to fight the pro-independence campaigns, though some analysts believe a coordinated effort could end up inflaming Catalan and Scottish opinion, instead.
The debate is being watched well beyond Europe. Far-flung states such as Russia and China with restive minority populations are concerned that the breakup of a major European state could fuel separatist feeling at home.
British and Scottish officials say they have already received queries from their U.S. counterparts on the issue and say Washington is noticeably lukewarm about the prospect that two key NATO allies might be about to radically change.
Fiona Hill, a former official at the U.S. National Intelligence Council and now head of the Europe programme at the Brookings Institution in Washington DC., says London and Madrid don't seem to realise how important this is seen to be beyond their borders.
"We are talking about two of the oldest states in Europe," Hill said. "I had a senior Balkan official ask me if it was the end of the multi-ethnic state."
If the unexpected happens and Scotland and Catalonia do vote for independence, no-one knows what it would mean in practice.
While those pushing for independence in both say they would want to remain within the European Union, most experts believe the new countries would have to apply for membership, which Madrid and London might be tempted to block, perhaps cutting them off at least temporarily from employment in the EU.
It is also unclear how an independent Scotland could continue to use sterling or Catalonia the euro, although in principle there would be no way for Britain or Spain to stop them. National debt and natural resources, from water rights to Scotland's share of North Sea oil, would all have to be negotiated.
If Catalonia votes for independence but Madrid attempts to block it from splitting off, long-simmering resentment on a host of issues could spill out into violence on the streets.
So far, however, the biggest lesson from these independence movements appears to be a positive one: they have been relatively effective while remaining peaceful, compared to more violent separatists such as the IRA in Northern Ireland or ETA in Spain's Basque country.
"If that was the first lesson of this decade of the 21st century, I think that would be a beautiful thing," says Catalan separatist politician Bosch. (Additional reporting by Braden Phillips in Barcelona; Editing by Sonya Hepinstall)