It will not be the first such referendum. In 2014, a Catalan self-determination referendum was held in November that year. While more than 80 per cent supported Yes, turnout was estimated at between only 37 and 42 per cent due to a boycott by those opposed to independence.
With the Spanish conservative government of Mariano Rajoy saying such a vote is illegal, in breach of the Constitution and must not take place, tensions are being ratcheted up between Madrid and Barcelona.
Catalan ministers responsible for the 2014 effort have been prosecuted and, in some cases, barred from office. The head of Catalonia’s police force recently resigned.
The Catalan government, under Carles Puigdemont, insists that the process will go ahead and should there be a Yes vote, the process to create an independent republic will begin within 48 hours.
To ensure this, the government have been putting the structures in place for a potentially independent state, including a tax and revenue agency and the outlines of a diplomatic service.
Recent opinion polls show a majority in the region favour holding a referendum on secession, but the debate has largely focused on the right to hold a referendum, rather than the details of the independence prospectus itself, such as the economic and social aspects.
Support for independence has been growing in Catalonia for the last decade because of complaints that it pays too much into the Spanish coffers, and because a reformed devolution statute was undermined by the Constitutional Court in 2010.
Some polls have put support at over 50 per cent, but mostly it is in the mid-40s. However, most Catalans would settle for less – a new financial settlement; more autonomy; recognition as a nation; and guarantees for their language. It is the refusal of Spain to concede that drives many people from what in Scotland is called ‘devo-max’ to ‘independence-lite’.
If the vote takes place and there is a Yes majority, the Catalan government hopes for international recognition, starting with European states. They also hope to start governing, building on their own state structures, requiring people to pay their taxes to Catalonia instead of Spain.
With Spain only recently dropping threats to block independent Scottish membership of the European Union, it is only natural that the SNP government will be proceeding with caution over the referendum. Should the vote go ahead on 1 October, the party has claimed that it will be prepared to congratulate whoever is victorious
It will require a convincing mandate to give the result the legitimacy it requires, and that will require unionist parties to actively campaign and for their voters to turn out.
Without this, it will be seen as just another protest vote.
Alex Orr is managing director of Orbit Communications, Edinburgh.