The referendum in favour of greater autonomy for Catalonia within Spain lays down its political identity for the coming generation and sets the scene for future negotiations with Spain's other 16 regional authorities.
Catalonia is the country's most prosperous and developed region, whose five million people produce a high proportion of Spain's national wealth. This agreement gives it greater powers of self-government, more control over its finances, and a bigger say in determining infrastructural, transport and immigration decisions. After much argument, a compromise describes Catalonia as a nation in the preamble, rather than in the complex 57 pages of the statute's text, which has 227 different clauses. This displeased right-wing Spanish nationalists - who say the document still sets dangerous precedents for breaking up Spanish unity - and left-wing separatists who resigned from the regional coalition in protest.
The agreement must be understood against the background of Catalonia's long independent history and the oppressive centralist control of the late dictator, General Franco. Other regions do not have precisely the same levels of autonomy, in recognition of their differential relations with Madrid. Attention will now turn to the Balearic islands, Andalusia and Galicia, where demands for greater regional powers have been made based on the Catalan example.
Above all, this agreement sets the scene for expected talks between prime minister José Luis Rodríguez Zapatero and the armed Basque separatist group Eta. Its announcement last March that it would observe a permanent ceasefire has so far been delivered upon, opening the way for negotiations to explore whether the ban on Batasuna, the political party which supports Eta, can be lifted so it may participate in elections next year. There is growing optimism that an overall Basque agreement short of secession can be reached, inspired by the Catalan example and the Northern Ireland peace process.
If so, Mr Zapatero will have carried off a remarkable feat in Spanish politics, laying the ground for his possible return to office after the next elections. He has been prepared to take political risks to deliver on a radical agenda and has reaped the benefits of it - helped by a buoyant economy and a construction and property boom that rival Ireland's. He has broad public support so far, but will need to be cautious and calculating in his handling of the Basque issue to retain it. The opposition Partido Popular's strident denunciations of the Catalan and Basque initiatives as a threat to national unity have rebounded, boosting Mr Zapatero's overall popularity.