Events in the French capital last week during Paris Saint-Germain's Ligue 1 title celebrations were a serious blow to the prestige of the club's Qatari owners and brought the issue of football-related violence back to the top of the agenda in the country.
Pictures of the destruction caused by troublemakers and of their clashes with riot police were seen all across the world last Monday night, completely removing the focus away from PSG's on-field success.
What the bemused PSG players and staff must have thought as they were ushered away from the stage set up for them at Trocadéro, across the Seine from the Eiffel Tower, can only be imagined, although coach Carlo Ancelotti's reaction two days later offered an insight.
"It was disappointing for me and for everyone who likes PSG," said the Italian. "At the time, we didn't understand what was going on, there was a lot of confusion. We were there for 10 minutes and only learned exactly what had happened once we returned to the Parc des Princes. I have never seen that before."
The club were not slow to give their reaction to the events, which led to dozens of arrests. They issued a statement, describing the troublemakers as having "nothing to do with football and even less with those that fill the Parc des Princes on matchdays with such passion and enthusiasm and in total security."
They added that PSG are "more determined than ever to build a huge European club, worthy of the French capital, and far removed from those intent on trying to destroy that dream."
The club's discourse was understandable. However, it cannot really be claimed that none of the troublemakers were PSG fans, even if the term 'fan' is applied loosely. Indeed, the first man to be convicted of involvement, a 27-year-old from the city's upmarket 8th arrondissement, was still wearing his PSG replica kit when he appeared in court last Wednesday to receive a two-month prison sentence for throwing glass bottles at police.
In the immediate aftermath of the violence, police claimed that many of those involved belonged to radical former ultra groups that gathered at the Auteuil end of the Parc des Princes before being banned when former PSG president Robin Leproux decided to sanitise the stadium in 2010.
This column was at the PSG-Marseille clash in February 2010 that was overshadowed by the death of a supporter in pre-match violence between rival Paris fan groups. The murderous violence outside the ground beforehand was accompanied by a thoroughly poisonous atmosphere inside the stadium that night.
Three years ago, it appeared more likely that PSG would be shut down by the government than become a leading player on the European stage once again. Leproux knew the gravity of the situation and sought to make the ground more family-friendly.
The measures he took, notably banning 13,000 supporters from renewing their season tickets, were controversial. However, they were in many ways successful. The ground is now a safer place, even if the atmosphere has lost a lot of its former edge.
Many of those who have been banned believe they were unfairly targeted, and last week's title celebrations at Trocadéro were the perfect chance for them to publicise their disquiet. A banner proclaiming "Liberty for the Ultras" could be seen amid the crowds.
Had the celebrations taken place at the Parc des Princes, none of this would have happened. But Qatar Sports Investments (QSI), who took over PSG in 2011 with Nasser Al-Khelaifi replacing Leproux as president, wanted to stage the event with the Eiffel Tower in the background. It should have been the perfect photo opportunity, the ideal way to boost their image.
Fan violence is not simply a problem for the champions, though. That was made quite clear on Saturday, when clashes took place between fans of Marseille and Lyon as their buses passed each other at a motorway toll.
OM fans heading to their team's game in Saint-Etienne fought with Lyon fans returning home following the postponement of their match in Nice. Seventeen people were injured, leading France's Interior Minister Manuel Valls to comment: "Such serious incidents show that football is still ill."
In Paris, things have changed considerably in the years since 'Plan Leproux' was implemented. But last week's troubles were an unpleasant reminder of the dangers bubbling under the surface for PSG's Qatari owners. Along with the inevitable search for a new coach, it is another thing to worry about for the powers-that-be at the Parc des Princes.