It has been rumbling away for months, but on Monday the long-running dispute between Manchester United manager Sir Alex Ferguson and shareholder John Magnier blew wide open.
What exactly is going on at Britain's biggest club, how did the row start and what might happen to Ferguson?
What is the row about?
John Magnier and his partner JP McManus, whose company Cubic Expressions owns more than 25% of the Premiership champions, have threatened to call an extraordinary general meeting at the club.
Ferguson's fall-out with Magnier has been spectacular
The pair have sent letters to the United chairman Roy Gardner and chief executive David Gill raising concerns about how the club is run.
Although the last letter was seven pages long and contained 63 separate headings, the key point is whether Ferguson should be offered a new four-year contract worth £4m.
Magnier and McManus are pushing instead for a rolling one-year deal - an option which would infuriate Ferguson, who is ready to sign the existing deal.
The two Irishmen have also demanded an investigation into how recent big-money transfer deals were conducted.
Is that it?
Not at all. There is also a very bitter row between Magnier and Ferguson over the ownership of racehorse Rock of Gibraltar.
Ferguson claims that, in August 2001, representatives of Magnier offered him a half-share in the horse. Magnier maintains that Ferguson was merely offered five per cent of any race prize money the horse won.
Why does this matter? Because Rock of Gibraltar subsequently won seven successive Group One races, and is now expected to make around £150m in stud fees - tax-free - over the next few years.
In other words, Ferguson and Magnier are arguing over £75m - an enormous sum of money, even when you have been managing Man United for 18 years.
What happens now?
Ferguson has begun court proceedings in Dublin to attempt to recover some of the money he feels he is owed.
Magnier is one of the richest and most influential men in Ireland
Whether the case actually makes it to court is another matter. Both men would rather settle before then, but neither is prepared to back down - which complicates matters at United.
From Ferguson's point of view, although he was registered as co-owner of the Rock with Magnier's wife Sue, no written contract was ever signed giving him half the stud fees, and he did not pay a penny for either his half-share or training fees.
So it would come down to one man's word against another.
Magnier's friends say that he did not become a billionaire by giving away millions of pounds as a gesture of friendship towards football managers he has just met.
His actions with United the last few days, while completely legitimate for a man with such a large investment, are being seen by Ferguson's supporters as acts of brinkmanship aimed at persuading the Scot to back down in the court case.
Could Ferguson lose his job as manager of United?
In theory, yes. Magnier and McManus are close to having enough shares to be able to force a takeover. Even if they do not, they remain the most powerful shareholders currently at the club.
In reality Ferguson's position remains safe. It is more a question of how long his contract extension will be.
It makes no sense for men with such a huge financial stake in United to want to get rid of the most successful manager in the club's history.
If Ferguson left, United's share price would plummet - leaving major shareholders seriously out of pocket.
United's future success on the field - and by association its financial health - is too bound up with Ferguson for anyone with a big stake in the club to want him out.
Could the whole messy business still end peaceably?
It depends on whether a settlement can be reached.
If neither party backs down - and both parties are used to getting their own way - the dispute could escalate still further in the coming weeks.
And with Ferguson needing to devote all his concentration to United's Champions League and Premiership campaigns, that would spell bad news for all concerned.