Sir Alex Ferguson has lifted the lid on life behind the scenes during his 26 year career in charge at Manchester United in his new autobiography - and revealed how he had explosive bust-ups with former stars Roy Keane and David Beckham.
Keane was captain of perhaps Ferguson's greatest Manchester United side but was never far from controversy, and left under a cloud in 2005 after he gave an interview to MUTV - which was subsequently pulled by Ferguson - in which he criticised some of his team-mates.
In his book 'My Autobiography' he claimed Keane, who made 480 appearances for for Red Devils, thought he was "Peter Pan" and said: "It was unbelievable. He slaughtered everyone. Darren Fletcher got it, Alan Smith. Van der Sar. Roy was taking them all down.
"I told him 'What you did in that interview was a disgrace, a joke. Criticising your team mates and wanting that to go out.'
"Roy’s suggestion was that we should show the video to the players and let them decide."
In his book, which is released later this week, Ferguson insisted Manchester United did right by Keane by paying off the rest of his contract and offering him a full testimonial.
Ferguson goes onto describe what he calls one of the most 'uncomfortable' moments of his life, before adding: “He has the most savage tongue you can imagine.”
He writes: "The hardest part of Roy's body is his tongue, He has the most savage tongue you can imagine. He can debilitate the most confident person in the world in seconds.
"With Roy, there were episodes of great friction and dramas he tried to impose his will on the team. On one occasion, as I came in to the dressing room, Roy and Ruud van Nistelrooy were at it, hammer and tongs. They had to be pulled apart by the players. At least Van Nistelrooy had the courage to stand up to Roy, because not everyone did. He was an intimidating, ferocious individual. He mode when angry was to attack, lay into people.
"I believe - and [assistant] Carlos Queiroz was at one with me on this - that Roy Keane's behaviour patterns changes when he realised he was no longer the Roy Keane of old. We're certain of that. Acting on a conviction that some of this strengths had been stolen from him by injury and age, we tried to change his job description, for his benefit as much as ours."
Govan-born Ferguson, who called time on his glittering career as Manchester United manager over the summer having won 13 Premier League titles and two Champions League trophies, was also critical of David Beckham, who left to join Real Madrid in 2003 after becoming the world's most recognised player at Old Trafford.
The Scot also believes Beckham made the wrong decision in opting to move to LA Galaxy from Madrid 2007.
"It would be churlish of me to say he made the wrong decision in the sense that he is a very wealthy man," he writes.
"But I am a football man and I don’t think you give up football for anything...The only thing making him a legend at LA Galaxy and beyond was his iconic status. At some point in his life he may feel the urge to say: I made a mistake."
Beckham emerged as part of the golden generation of youth players at Old Trafford alongside the likes of Paul Scholes, Nicky Butt and the Neville brothers, and went on to help the Red Devils win the Champions League in 1999 and six league titles between 1996 and 2003.
Ferguson, who has previously been critical of Beckham's celebrity marriage to Spice Girl Victoria Beckham, says his star status went to his head.
"The minute a Manchester United player thought he was bigger than the manager, he had to go," he wrote. "David thought he was bigger than Alex Ferguson.
"That was the death knell for him."
He continues: "David was the only player I managed who chose to be famous, who made it his mission to be known outside the game," wrote Ferguson. "I felt uncomfortable with the celebrity aspect of his life."
Ferguson also recounts a tale of when he tried to get Beckham to remove his hat during a pre-match meal, with the former England captain reluctant to do so because he wanted to unveil his new haircut no the pitch in a game against Leicester City.
“He went berserk,” he said.
He continued: “He would have been one of the great Manchester United legends.”
Beckham was at the centre of one of the more contentious issues of Ferguson's reign when, in 2003, the retired manager cut the midfielder's face by kicking a football boot at him.
"In his final season with us, we were aware that David's work rate was dropping and we had heard rumours of a flirtation between Real Madrid and David's camp. The main issue was that his application level had dropped from its traditionally stratospheric level.
"He was around 12 feet from me. Between us on the floor lay a row of boots. David swore. I moved towards him, and as I approached I kicked a boot. It hit him right above the eye. Of course he rose to have a go at me and the players stopped him. 'Sit down,' I said. 'You've let your team down. You can argue as much as you like.'
"The next day the story was in the press. In public an Alice band highlighted the damage inflicted by the boot. It was in those days that I told the board David had to go.
"My message would have been familiar to board members who knew me. The minute a Manchester United player thought he was bigger than the manager, he had to go. I used to say, 'The moment the manager loses his authority, you don't have a club. The players will be running it, and then you're in trouble.'"
Keep checking GiveMeSport for all the latest revelations from Sir Alex Ferguson's "My Autobiography".