Today’s tales from two cities diverge as sharply as ever. One tale and one city is Edinburgh, where Scottish politics have their own dynamic; the other city is London, full of feverish speculation, absorbed by the question of when Tony Blair will step down as PM. But the two, linked cities that cry hardest for attention are the cities where devolution’s pull is fiercest, where nationalism exerts the next stage of logic. Welcome to Madrid (approached via Barcelona).

It’s fascinating to visit Edinburgh and then go on to the capital of Catalonia, as I’ve done in the past few weeks. One is busy with devolved politics and preparing for elections next May, which — on current forecasts — will make a Scot Nat first minister in Holyrood. The other, having extracted far greater powers and the legal language of “nationhood” from Spanish central government, is settling down for another round of polls this year. Is devolution on this level a point where the separating can stop? Is the current Catalan settlement a perfect model for Europe? Is there a steady state for mini-states within a state? The Catalan moderates who, in Barcelona, thought the latest deal a decent bargain are replaced here by Castilian moderates who fear much worse. They don’t see the thirst for independence — in the Basque country or Catalonia — being quenched for long. It’s a terrible contradiction. The more we live in a globalised world without economic borders, the greater the desire to live in little national boxes.

There are special factors in play here. One is language, the driving force both of Franco’s repression of the Catalans and modern Catalonia’s separation. Can you (my Castilian friends ask) teach Catalan first and best in Catalan public schooling without condemning a generation of young people to speak and write Castilian too poorly to fit them for jobs in the rest of Spain? Here’s the slippery slope towards less investment and gradual economic decline. Here are the ties that should bind being torn apart.

Now, you may think this alarmist. When the talk is about France and residual Spain vetoing Catalan membership of the EU, you can see an issue spiralling beyond rational analysis. But that’s not quite the end of the story. Devolution has been a bit of bore for residual England. Our frustration was more about Belfast’s continuing failure to govern itself than over Edinburgh and Cardiff’s assumption of that burden.

The Scots have been very successful in running their own affairs. If they wanted to do much more, within the EU, that would surely be possible in the end. Nationalism isn’t always destructive. But it is dangerous when treated carelessly, whenever left to the fiercest believers. Is David Cameron right to stir this murky pot? Will a Scottish PM in London be best placed to deal with it? Why should London want Blair to go before next May, so that Gordon Brown has that crisis on his hands straight away? The difficulty is how completely two cities, and two perspectives, fail to meet. The difficulty is Madrid as well as Barcelona. — The Guardian