Tens of thousands of people gathered in Madrid on Sunday to protest against the government’s handling of the Catalan question, as the country braced for the landmark trial of 12 separatist leaders this week.

About 45,000 people joined the rally in Colón square to vent their fury at what they see as the overly conciliatory stance adopted by the prime minister, Pedro Sánchez, and to demand a snap general election.

The demonstration was called by the conservative People’s party and the centre-right Citizens party, and backed by the far-right Vox party. It also attracted some supporters of fascist and extreme-right groups.

The key figures in the push for Catalan independence Read more

The protest came two days before the beginning of the trial of separatist leaders behind the failed bid for regional independence, an event that provoked Spain’s worst political crisis since it returned to democracy after the death of Franco.

The public proceedings at Spain’s supreme court, which are expected to last three months and which will be broadcast on television, will focus on the independence referendum held in October 2017 and the regional parliament’s subsequent unilateral declaration of independence.

Nine of the defendants - who include the former Catalan vice-president Oriol Junqueras, the former speaker of the Catalan parliament Carme Forcadell and two influential grassroots activists, Jordi Cuixart and Jordi Sànchez – are accused of rebellion, which carries a prison sentence of up to 25 years. Other charges include sedition and the misuse of public funds.

Facebook Twitter Pinterest The former Catalan vice-president Oriol Junqueras. Photograph: Lluis Gene/AFP/Getty Images

At the heart of the case will be the then Catalan government’s decision to hold the referendum despite repeated warnings that it would violate the constitution, which stresses the “indissoluble unity of the Spanish nation”.

Although Catalan pro-independence parties have never managed to win 50% of the vote in the regional parliament, and although polls consistently show Catalonia is roughly evenly split over the independence issue, the government of the then Catalan president, Carles Puigdemont, chose to press ahead with the vote.

Pro-independence parties managed to get a law paving the way for the referendum passed in the regional parliament in early September 2017, despite furious objections from opposition MPs who complained that usual procedures had been disregarded.

Three weeks later, on 1 October, the Catalan government held the referendum, which was marred by violence from Spanish police officers who raided polling stations, charged crowds with batons and fired rubber bullets as they tried to stop the vote.

Facebook Twitter Pinterest Spanish riot police clash with people outside a polling centre in Tarragona on the day of the referendum. Photograph: Jaume Sellart/EPA

According to the Catalan government, about 2.3 million of Catalonia’s 5.3 million registered voters – 43% – took part in the referendum, and around 90% of participants backed independence. The vote was largely boycotted by unionist Catalans.

On 27 October, shortly after secessionist Catalan MPs voted to declare independence, the Spanish government of the then prime minister, Mariano Rajoy, won senate backing to sack Puigdemont and his cabinet and assume direct control of Catalonia.

Puigdemont fled into exile in Belgium days later, while Junqueras and seven other former Catalan ministers were remanded in custody.

The president of the supreme court, Carlos Lesmes, has described the proceedings as “the most important trial that we’ve held since democracy [returned]”.

Hundreds of witnesses are to be called, among them Rajoy, his former deputy, Soraya Sáez de Santamaría, the mayor of Barcelona, Ada Colau, the former Catalan president Artur Mas and the current speaker of the Catalan parliament, Roger Torrent.

Facebook Twitter Pinterest The former Catalan president Carles Puigdemont. Photograph: Niall Carson/PA

The court has ruled that Puigdemont will not be allowed to testify via videolink from Belgium. Other witnesses will include some of the Catalan voters and Spanish police officers injured on the day of the referendum.

Both the Spanish and Catalan governments are acutely aware of the publicity and scrutiny the trial will bring. Catalan independence leaders are keen for their day in court as a means to mobilise their grassroots supporters after months of inertia and as fractures grow within the movement.

They have repeatedly sought to accuse the Spanish justice system of institutional bias and to claim that the accused are being punished for defending the right to self-determination.

In a recent interview, Puigdemont told the Associated Press that the trial would be “not an act of justice but rather one of vengeance”, while his handpicked successor, Quim Torra, has argued that no crime has been committed.

Sánchez’s socialist government has been embarking on its own PR campaign to counter the claims of the pro-independence faction. The prime minister has consistently argued that a clear separation of powers exists in Spain, and that the judiciary is wholly independent of the government. The prime minister visited the European court of human rights in Strasbourg last Thursday to stress Spain’s commitment to the rule of law.

The Sánchez administration has pointed to a series of high-profile court cases as further evidence of a fully functioning and impartial legal system. The former deputy prime minister Rodrigo Rato was sentenced to four and a half years in prison in February 2017 for misusing corporate credit cards while in charge of two leading Spanish banks at the height of the country’s financial crisis.

The brother-in-law of King Felipe is serving a six-year prison sentence after being found guilty of charges including embezzlement, fraud and tax evasion. The king’s sister, Princess Cristina, was cleared of helping her husband evade taxes at the end of the same trial two years ago.

By far the most dramatic court case of recent years, however, was the so-called Gürtel trial. Spain’s highest criminal court ruled in May last year that the People’s party, which was then in government, had profited from an illegal kickbacks-for-contracts scheme. The judges expressed doubts over the credibility of the testimony offered by Rajoy the previous July, when he became the first serving Spanish prime minister to give evidence in a criminal trial.

The Gürtel verdict prompted Sánchez to bring a motion of no-confidence against Rajoy and his government. The vote that removed Rajoy from office and installed the socialist party as a minority government was successful only because it won the backing of the Basque Nationalist party – and the Catalan pro-independence parties of Puigdemont and Junqueras.