Sir Alex Ferguson has lifted the lid on his feud with Roy Keane, with the Scot claiming his authority at Manchester United would have been undermined had he not sold the increasingly volatile player in 2005.
Ferguson revealed on Tuesday that Keane "slaughtered" several of his team-mates in an interview for United's in-house channel MUTV.
The interview came following United's 4-1 defeat to Middlesbrough in October 2005. He was released by the club the following month and joined Celtic.
Ferguson reveals in his soon-to-be-published autobiography that Keane invited the United players to watch the interview, which has never been broadcast.
The decision backfired as several senior players, including Edwin van der Sar and Ruud van Nistelrooy rounded on the Red Devils captain.
Keane then accused Ferguson of bringing his own dispute with shareholder John Magnier over the Rock of Gibraltor racehorse into the club.
That proved to be the last straw for the fiery midfielder.
"Given the nature of the man you can expect a response. That is the type of personality Roy is," the former United boss said in a press conference to publicise 'My Autobiography', which is out on Thursday.
"We had to react to the situation so quickly because his actions were so quick. For one reason or another he decides to go and criticise his team-mates.
"Most of you won't have seen the video but you couldn't release it. You just couldn't.
"It ended up with two of our young players being booed before a Champions League match in Paris because of it.
"We decided we had to do something. The meeting in the room was horrendous. I just couldn't lose my control in this situation.
"If I had let it pass and allowed it to happen the players would have viewed me differently. Much more differently to how I would have liked to have been judged.
"Throughout my career I have been strong enough to deal with important issues like that. Roy overstepped his mark. There was no other thing we could do."
In the book, Ferguson colourfully recalled how intimidating Keane could be when he was on the warpath.
"What I noticed about him that day as I was arguing with him was that his eyes started to narrow, almost to wee black beads. It was frightening to watch. And I'm from Glasgow," Ferguson wrote.
Ferguson reveals in the book that Keane turned up at Carrington months later to apologise for his conduct.
Ferguson made Keane captain not long after his British record move from Nottingham Forest in 1993, and by the time the MUTV interview had taken place, the Irishman had already caused controversy with a brutal tackle on Manchester City's Alf-Inge Haaland.
Ferguson reveals in his book that he had doubts about the player in the summer of 2005.
Then, Keane complained vociferously about the standards at the club's base for their pre-season training camp in Portugal.
Despite criticising the player in his book, Ferguson will never forget the midfielder's efforts on the pitch for United, with whom he won seven league titles.
"We did well by him," Ferguson added in his press conference.
"We paid up his whole contract. We gave him a testimonial the following season and there were 75,000 there. We did everything we could to honour the fact he was a great player for us."
Ferguson and Keane clashed again in 2011 when the latter criticised United's early exit from the Champions League.