Racism, a problem that English football thought it had solved, has returned to haunt the country that gave birth to the game, with the Premier League's global popularity on the line after a succession of scandals.
With Luis Suarez and John Terry having already earned bans for racist abuse, the issue lurched into new territory on Sunday when top flight referee Mark Clattenburg was accused of racially abusing Chelsea's John Mikel Obi.
It came after a match between Chelsea and Manchester United that had been a memorable encounter, full of incident and intrigue, but when the accusations against Clattenburg emerged a few hours later, the mood soured.
The seriousness of the claims was not lost on commentators on Monday.
"If a match official has used racial insults or language to a player, then he's for the high jump," former Premier League referee Jeff Winter told BBC radio. "It'd probably be the end of his career, if proven."
The allegations are being seen as all the more shocking because English football was supposed to have banished the monkey chants and banana-throwing of the 1970s and 1980s during the period of aggressive gentrification heralded by the launch of the Premier League in 1992, as ticket prices and television exposure soared.
England came to be seen as a safe haven for black footballers and by 2002, Arsenal were fielding teams containing as many as nine black or mixed race players.
When English teams have found themselves the target of racial abuse, it has been portrayed in the national media as a problem that now belongs to other parts of the world.
After footage emerged of England's Danny Rose being taunted with monkey noises by fans during an under-21 match in Serbia earlier this month, the shock reflected the fact that such scenes have not been witnessed in England for decades.
When Uruguayan striker Suarez was accused of racially abusing United's Patrice Evra last season, meanwhile, it was held that he was simply unprepared for the sensitivities of life in a multi-cultural society.
The Suarez case, though, proved to be the tip of the iceberg.
The Liverpool striker was banned for eight matches but it was followed by the Terry-Anton Ferdinand affair, several accusations of racial abuse by fans towards players on social media, and now the claim that Clattenburg used a racist insult against Nigerian midfielder Mikel at Stamford Bridge on Sunday.
But if racism now seems to be back on the agenda in English football, John Barnes -- a target of the banana-throwers of the 1980s -- says that it never went away.
"It's very easy to call it social injustice when it affects us -- with Danny Rose, with Anton, with Luis Suarez -- but what about the social injustices that go on for black people every day?" the former Liverpool winger asked talkSPORT radio last week.
"There's no way we can get rid of racism in football if it exists in society."
The Premier League is a worldwide marketing phenomenon, but the sponsors and fans may find it hard to remain loyal if the flagship of the English game comes to be seen as a place where discrimination is allowed to fester.
Leading black players have already made their feelings known, with Reading striker Jason Roberts leading a boycott of the "Kick It Out" T-shirt campaign that prompted the Professional Footballers' Association to issue an anti-racism action plan.
That Chelsea -- a club scarred by racism allegations after their captain, Terry, was banned for abusing Anton Ferdinand -- should make such claims against Clattenburg suggests they have full confidence in their case.
After receiving criticism over its handling of the Suarez and Terry affairs, the Football Association has no choice but to investigate Chelsea's complaint with the utmost speed and transparency.