Towards the end of 2017, Manchester City manager Pep Guardiola began to wear a yellow ribbon on his chest.
He wore it to press conferences and also on the side of the pitch in both the Premier League and Champions League.
It soon became a talking point as supporters and the media wondered what it meant and why he wore a yellow ribbon. Some of his rivals even passed comment.
Managers and footballers wear all sorts of symbols on their chests, but what exactly is Guardiola's all about? Goal takes a look.
Why does Guardiola wear a yellow ribbon?
Guardiola wears a yellow ribbon as a gesture of support for imprisoned activists and politicians who campaigned for Catalan independence.
Jordi Sanchez and Jordi Cuixart, leaders of Assemblea Nacional Catalana (ANC) and Omnium respectively, were jailed, along with a number of members of Carles Puigdemont's deposed Catalan government following their role in the unsuccessful push for Catalan independence from Spain back in October 2017.
The Manchester City boss has long been a vocal proponent of Catalunya seceding from Spain and has been heavily involved in promoting the movement.
He went into some depth on the issue back in November following their imprisonment, explaining that he hoped that he would not have to wear it for long but insisted that he will wear it as long as they remain detained.
"I hope that the politicians in prison can leave as soon as possible for their families," Guardiola told reporters. "If it can happen to them then it can happen to us. For giving an opinion. People shouldn't be confused and think it couldn't happen to them, because it can."
The former Barcelona boss added: "We cannot ignore that these eleven politicians or activists, who haven't hurt anyone, are in prison for asking to vote.
"Many things have happened but it's all because we wanted to vote, because we wanted a legal referendum. The solution is that the state and Catalunya should agree and we can have an agreed referendum. It's as simple as that."
Is Guardiola allowed to wear a yellow ribbon?
The short answer to that is: it depends on who you ask, since governing bodies appear to have different policies regarding such matters.
Guardiola's long-time foe Jose Mourinho stoked the embers of their rivalry ahead of the Manchester derby in December when he suggested that the Catalan coach may not be allowed to wear the ribbon.
"I think that our political ideology and our political beliefs is something that we have the right to have," Mourinho told reporters. "I've known Pep for many years, I think I know what Pep feels about his country. To have [politics] in football, I don't know the rules.
"If the rules allow us to do that, he is a free citizen to do it. But I am not sure if the rules allow any political message on the pitch. That's just my doubt."
Guardiola responded to Mourinho's attempt to get under his skin by doubling down on his principles, stressing that he would accept any punishment that came his way. The City boss said: "They want to suspend me, UEFA, the Premier League, FIFA, it's OK. I will be suspended."
The Football Association (FA) decided to take action in February, releasing a statement to confirm that Guardiola had been charged for breaching kit and advertising regulations, before fining the City boss £20,000 in March and warning him over his future conduct.
In the days prior to the fine being issued, Guardiola accepted the FA charge of "wearing a political message", putting him in breach of the organisation's kit and advertising regulations.
The brief statement issued by the FA read: "Manchester City manager Pep Guardiola has been fined £20,000 and warned as to his future conduct after admitting an FA charge for wearing a political message, specifically a yellow ribbon, in breach of The FA’s kit and advertising regulations." 
Despite previously reprimanding the Catalan, he defied them once again by wearing the ribbon at the Carabao Cup final, in which his side defeated Arsenal to lift the trophy. Afterwards, Guardiola doubled down on his stance on the ribbon and the Catalan independence movement, drawing comparisons with Brexit and the Scottish Independence referendum.
The wearing of a yellow ribbon by Guardiola is not something that is strictly catered for in the FIFA or UEFA regulations, so there is somewhat of a grey area. However, the display of political symbols, slogans and images on players' shirts is specifically dealt with.
Law 4.5. of the International Football Association Board (IFAB) Laws of the Game, which relates specifically to players' equipment (i.e. shirts, boots and so on), states that equipment "must not have any political, religious or personal slogans, statements or images."
The law adds: "Players must not reveal undergarments that show political, religious, personal slogans, statements or images, or advertising other than the manufacturer`s logo. For any offence the player and/or the team will be sanctioned by the competition organiser, national football association or by FIFA."
This particular law recently caused uproar in the United Kingdom when the four British associations (FA, FAW, IFA and SFA) were fined for displaying a commemorative poppy on their shirts during World Cup qualification games that occurred during a period of remembrance for Armistice Day.
UEFA has similarly cracked down on the display of imagery or banners by supporters that are perceived to be of a provocative or political nature, with Celtic supporters , for example, frequently falling foul of the European governing body's rules in that regard.
What is Catalan independence & why is Guardiola involved?
The Catalan independence movement is a socio-political phenomenon which seeks the secession of Catalunya from Spain and the establishment of a fully autonomous Catalan republic.
In October 2017, the Catalan government, led by Puigdemont, pushed for a referendum on the issue and subsequently sought to establish an independent state. However, the moves were declared to be illegal by the central Spanish government and quashed.
A native of the region, Guardiola is passionate about his identity and has even represented the Catalonia national team. He has been one of the independence movement's prominent supporters for quite some time and has spoken at a number of rallies, consistently urging the need for dialogue and the recognition of democratic principles.
"It's a really sad day for democracy. I thought in the 21st century, those kind of things didn't happen," he said following the escalation of the crisis in the region in October . "Especially, for example, the Catalan parliament is older than the Spanish parliament itself.
"I am really, really sad. The Catalan people just wanted to vote and we want to be listened to and let the people say what they wanted to be [part of Spain or independent]."
Guardiola described the imprisonment of Sanchez and Cuixart following the failed independence push as a scary development . "It's a little bit scary," he said. "We are going backwards in a democratic state, that we have regressed so much in the rule of law."
Thus, the decision to wear a yellow ribbon is merely a continuation of his long-held solidarity for those who, like him, wish to pursue the idea of an independent Catalunya.