EXACTLY one week before the Scottish independence referendum, central Barcelona witnessed what was probably the biggest political demonstration ever seen in Europe. On Catalan National Day, September 11, 2014, around two million people turned the city into a seething ocean of red and yellow – interspersed with a fair few blue-and-white saltires – to proclaim their support for their country’s independence.

The following month, I was invited by pro-independence activists, who had been inspired by Scotland’s Yes movement and Women for Independence in particular, to spend a week in Catalonia. It was a gruelling trip, speaking at public rallies, giving media interviews, and having face-to face meetings with a range of individuals and organisations, including trade unions and four of the five pro self-determination parties.

I still remember a few of these events vividly. One was a public meeting in the centre of Barcelona with an all-woman platform and a mainly female audience, where one of the major themes was the link between women’s self-determination and national self-determination. Another was a moving ceremony in the grounds of the Seat car plant commemorating a worker shot dead by Franco’s Civil Guard during a 1971 factory occupation.

And then there was the illuminating discussion I had with the inspirational Carme Forcadell, the then president of the Catalan National Assembly, which represents 3000 civic organisations – who is now the presiding officer of the Parlament de Catalunya.

In the coming months, Catalonia will be back in the global spotlight – and this time the showdown between Barcelona and Madrid could have immense repercussions across Europe. The coalition government of Catalonia has called a referendum for Sunday, October 1 – and unlike the symbolic, consultative vote held a few years back, this is a serious bid for independence.

The question on the ballot paper is: “Do you want Catalonia to become an independent state in the form of a republic?” If a majority of people vote yes, the Catalan Government says it will make a unilateral declaration of independence within two days.

How this will play out is anyone’s guess. First, because, according to opinion polls, the result will be close. As things stand, there is a narrow majority for a No vote. But we live in volatile times. When Theresa May called the General Election she was 25 points ahead in the polls.

No-one expected Brexit. Three months before the Scottish independence referendum, some polls gave the No camp a 20-point lead, while three months before Brexit, one poll predicted a 14-point victory for Remain.

Even more unclear is whether the note will be allowed to go ahead.

The gap between the Yes and No camps in Catalonia may too close to call, but there is overwhelming support for a referendum. Polls have shown 70 per cent and more want the October vote to go ahead. This includes even some pro-union parties, such as the Catalan equivalent of the Greens, the Iniciativa per Catalunya Verds.

I met with one trade union leader in Barcelona who was against independence but vehemently in favour of a referendum.

BUT the governing party in Madrid, the right-wing People’s Party, has said it will block any referendum by any means necessary. It has even threatened to send in the troops to blockade polling stations and to close down the Catalan Parliament.

The Madrid government – and its feeble right-of-centre opposition in the shape of the Socialist Party — cites the Spanish constitution, which denies the right of any part of the multinational, multilingual state to secede. The constitution was approved in a referendum back in 1978, just a few years after the fall of Franco, when the granting of autonomous regional assemblies looked like a huge leap forward.

But times have moved on since the take-it-or-leave-it ballot which approved the constitution. No-one under the age of 60 in today’s Spain was able to participate.

So has this any relevance to the independence movement in Scotland? The National’s sister paper The Herald carried an article a few days ago by the respected David Leask, under the headline “SNP face diplomatic crisis as disputed Catalan independence vote looms”.

The piece carried a warning to the SNP from Professor Michael Keating of Aberdeen University, suggesting the party should be very cautious about provoking Spain because that could jeopardise Scotland’s chances of membership of the European Union. No disrespect to the veteran constitutional expert, but I hope the SNP and the wider Yes movement will ignore this particular advice.

The fundamental principle of the right of nations to self-determination must be at the core of our movement. To take any other stand on Catalonia would leave us justifiably open to the charge of slippery, self-serving hypocrisy.

Catalonia is older than the Spanish state. It had its own legal system and constitution as far back as the 13th century. At a time when Scottish home rule was denied by Westminster, a Catalan Parliament was established by the left-wing Spanish republican government in 1932, only to be smashed by Franco’s fascist regime in 1939.

The Catalan national movement, like its counterpart in Scotland, is profoundly internationalist and aims for independent statehood within the EU. It is likely to become a key ally of a future independent Scotland. And it has the right to choose its own future, no ifs, no buts.