Twelve Catalan politicians have gone on trial for their role in Catalonia’s failed 2017 independence bid, putting the spotlight back on Spain’s biggest political crisis in decades which could make it flare once again.

Catalonia defied a judicial ban by carrying out a referendum and subsequently unilaterally declaring independence in October 2017, to the dismay of much of the rest of Spain,.

There was shock at home and abroad when police used batons and rubber bullets on protesters on the day of the vote.

Some of the Catalan separatist leaders were later arrested or fled the country.

The start of the trial will refocus attention on the region’s push for secession which rattles Spain’s political and cultural identity.

The trial will decide if Catalan nationalist leaders stay in jail. The public prosecutor is seeking prison terms of up to 25 years on charges of rebellion and misuse of public funds.

At stake are Spain’s stability, the future of Catalonia’s independence movement as well as the region’s and the central government’s image abroad.

"It’s the most important trial we have had in democracy", Supreme Court president Carlos Lesmes told reporters on 1 February, referring to the return to democracy in Spain after dictator Francisco Franco’s death in 1975.

Explainer: Catalan leaders on trial over referendum

We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences

Raul Romeva, one of nine defendants jailed without bail since late 2017 facing the charge of rebellion, has made clear his view that it should end only with an acquittal.

"A (prison) sentence would weigh forever on history and on Spain’s future," Mr Romeva told the Reuters news agency in an interview conducted by email from jail.

At the time of his arrest, Mr Romeva was foreign minister in Catalonia’s regional government and a member of the European Parliament.

Fellow defendants include veteran Catalan politicians Oriol Junqueras and Carme Forcadell.

Notably absent from the list is former Catalan president Carles Puigdemont, who is in self-imposed exile in Belgium and thus cannot be tried in Spain.

Carles Puigdemont pictured at Trinity College during a recent visit to Dublin 

The dozen’s fate has been a rallying cry for separatists ever since 2017, said Federico Santi, analyst at political risk consultancy Eurasia, adding that he expected, like other observers, that the trial will re-ignite tensions.

Pro-Catalan independence protests had quieted down over the past months but separatist groups have called a series of protests in Catalonia and in Madrid to coincide with the trial.

Their supporters say they are political prisoners, while Madrid accuses them of breaking the law.