Sir Alex Ferguson's badly-timed autobiography damages both him and Manchester United

It is however largely his own players that bear the brunt of his famous hairdryer. In doing so he has divided United fans – some calling him brutally honest, others pointing out that the tone and targets were totally unnecessary.

United would not have had a Treble in 1999 had Keane not put on a spectacular one-man show to win them the Champions League semi-final against Juventus. In the final, Beckham took the corners from which United scored. Ferguson was knighted at the end of the year.

On target: Roy Keane, David Beckham

In assailing both players, Ferguson comes across as petty. His judgment – perhaps his greatest weapon as a manager – has let him down here. A judgment that was spot on nine times out of ten.

Remember this is the man who signed Robin van Persie when conventional wisdom told him to look for a central midfielder; he sold Beckham, to general disbelief; he persisted with a 4-4-2 for fifteen years, when the rest of Europe had moved far beyond it – and he still won, through instinct, street wisdom and a bit of luck.

This in turn built a veneer of invincibility. And that automatically extended to the organization he ran.

But aura, charisma and those other intangibles of personality are fickle. To build one takes time; to dent it takes one act of indiscretion.

This book is badly-timed and tarnishes his own legacy while casting a long, unforgiving shadow over Moyes as he struggles to create his own. It is hardly a smart move from a man who had stayed up by being watchful and second-guessing his opponents at every stage.

Let there be no two opinions about it: Ferguson plus Manchester United was greater than the sum of its parts and the separation, though inevitable at some point, has left both entities looking vulnerable.

Ferguson has chosen to further weaken both by hanging out the dirty linen in public. His achievements are permanent but, like a fallen Khal, the aura has developed a perceptible dent. And that is irrevocable.