Very seldom are we blessed with a perfect snapshot of career death ... an image, like the lachrymose Thatcher leaving Downing Street, that captures the precise moment at which a triple alpha human understands him- or herself to be history. On Wednesday, curiously, we saw two.
First we had Tony Blair looking unwontedly discomforted and pensive when David Cameron delivered that well- rehearsed off-the-cuff line that "he was the future once". Later in Lisbon, Sir Alex Ferguson trudged off towards the dressing room after Manchester United's disastrous defeat to Benfica bearing a similar expression of baffled defeatism, suggesting that the next time he picked up the electric hairdryer would be to invite it to share his bath.
On reflection, far from being curious, it seems almost inevitable that they enjoyed this rare burst of self-knowledge simultaneously. The parallels between them are so uncanny that I have come to suspect that they are osmotically linked via their mutual close friend Alastair Campbell, the parasite who hops between these twin hosts to effect a symbiosis of the kind wearily familiar to fans of The Twilight Zone and early Star Trek.
An entire doctorate, or even a sub-Jeffery Archer novel, could be written comparing their careers, but the brief highlights are these. Born and educated in Scotland, they rose to prominence in England at the beginning of the 1990s (front bench for Blair, first FA Cup for Fergie), rising through the decade and ending it at the apex of their powers (Blair was at his mightiest in 1999 when Sir Alex won his treble).
One gave the other his knighthood, the millennium came, and languidly at first the decline began. It must be the most ancient soap opera storyline of them all. The hero triumphs, is duly worshipped, swallows the legend of his own impregnability, and before you can say "Ajax" (Sophocles' rather than Cruyff's), the hubris turns into self-delusory dementia.
In each case, this expressed itself most graphically through the waging of a war that could not be won, Mr Blair taking on public opinion and the facts to play out of his league in Iraq, Sir Alex playing way above his by taking on a pair of ferocious Irish billionaires over the rights to a horse's semen.
From the second they picked these fights, Nemesis was on her way and the game was up. The billionaires, John Magnier and JP McManus, tormented Fergie with dirt dug by the fearsome investigators at Kroll; and then gleefully sold their shares in Manchester United to the Glazer family, which will shortly invite Sir Alex to depart his post. Of the disintegration of Mr Blair's reputation for competence and honesty, enough has been written already.
There are other parallels to keep the PhD student busy. Both had heart conditions surgically dealt with at much the same time (clearly the result of allowing Alastair Campbell into the bloodstream), and both had a monomaniacal, bully-boy favourite they over-indulged until he started publicly slagging off his colleagues. Eventually, again at the same time, our fallen titans showed the same clinical ruthlessness in discharging Roy Keane and David Blunkett respectively. Far from re-establishing their authority, however, the sackings exposed the true desperation of their positions.
In the dark hours since, they have clung to one another like the drowning men they are, Mr Blair telling an interviewer that the one manager he'd want in his Cabinet is Sir Alex. Which says as much about his judgement of a player's form as Sir Alex's purchase of Juan Sebastian Veron once said about his.
All of which brings us to Wednesday, that day of double epiphany, and to one of the great questions surrounding power. Why do they never know when to go? Why can they only, at most, flirt daintily with retirement (Fergie announced the date before reneging; Blair was talked out of it by his little cabal of Gordophobic ministers before coming up with that nebulous "before the next election"), but never join it under the duvet?
Most of them can't even flirt. Despite his great age and all those strokes, Churchill kept Eden waiting for aeons before being nudged aside. Margaret Thatcher could have gone covered in glory in 1989 after 10 years, but felt compelled to go on and on until she was an intolerable electoral liability, and Macmillan went when in deep trouble, and only then due to a misdiagnosis of prostate cancer. Harold Wilson is cited as the only modern PM to go voluntarily, but he was thoroughly exhausted by years of currency crises and baronial warfare within his Cabinet, and way past his sell-by.
It's the same in football. With the exceptions of Bill Shankly and Bob Paisley at Liverpool, it's hard to think of a great manager who has left at or near the top. Alf Ramsey should have quit in 1970 after the failure to defend the World Cup in Mexico, but was sacked after failing to qualify for the next one. Bill Nicholson was shunted out of Spurs more than a decade after producing the immortal Double-winning team of 1961, bequeathing a side poised for relegation. Brian Clough went one better, and took Nottingham Forest down before leaving to spend more time with his vodka.
You would no more have expected Clough or Ferguson to resign on the nights of their European Cup wins than Blair to have gone after the second landslide of 2001. No one, except maybe Ronnie Barker and Lennox Lewis, has the supreme wit and wisdom to leave the stage at their peak, with the crowd screaming "encore".
Yet to plough on for month after month, year after year, when every sentient being observing the drama sees that the situation is irredeemable, and that it can only become more dismal and humiliating ... to those of us with little ambition and no comprehension of what drives people to crave glory and dominion, it is perplexing in the extreme. Whether a metaphorical drug or a literal one (doubtless one can get hooked on psychoactive chemicals produced by the stress), pure power seems ultimately a far more destructive substance than pure heroin, which can be taken for ever without side-effects.
One of the nastiest side-effects of power is that absolute lack of self-awareness identified by Sophocles as the core element of tragic irony. So when the fallen hero begins to see himself as others see him, as Mr Blair and Sir Alex appeared finally to do on Wednesday, it must be a sure sign that the power is gone. In a sense, this is a shame. Lovers of schadenfreude would enjoy watching these twin souls squirm on the end of their nooses for another couple of years. But it won't be anything like that now. Much too late, they have seen the light at the end of the tunnel, and recognised it as the train.