Where's the ambition-driven KP of 2005?

On Sunday night, while England's cricketers were celebrating a victory that took them to a heady No. 2 in the one-day rankings, and while Royal Challengers Bangalore were thrashing Guyana in the first round of the Champions League, Kevin Pietersen - nominally an A-list member of both outfits - was sat on his sofa in Chelsea, watching The X Factor and laughing at an act called Bun'n'Cheese. As the bell-hop once said of George Best, where did it all go wrong?

Unlike Best, however, our knowledge of Pietersen's private life comes not from the agog reaction of a champagne delivery boy, nor - as is becoming all too common for sportsmen this summer - the front page of the News of the World. Rather, it has been gleaned from peering through the keyhole that is Twitter, the social networking phenomenon that may have earned KP a hefty slap on the wrists at a disciplinary hearing at Lord's last week but - aside from one sweary outburst - has been showcasing a touching degree of mundanity in the life of one of Britain's highest-profile sports stars.

In the current climate of scandal and exposé, Pietersen comes across as an exceptionally straight-laced sportsman. "Husband, daddy and proud English cricketer" is how he sums himself up on his Twitter page, and while there are plenty of cynics who would suggest that wording has been carefully chosen to play to his 49,000 "followers", many more would agree it is entirely in keeping with the unguarded stream of tittle-tattle, sports banter and general wibblage that flows from KP's keyboard on a daily basis.

If it's not Chelsea football updates, it's gripes about parking wardens or ponderings about restaurant choices, while from time to time Pietersen's young son Dylan is referenced, as if to underline a sense of domestic contentment far removed from the frustrated stagnation of his international career. "On my way to work now ..." he tweeted on the second morning of the Oval Test, having fallen for 6 on the previous day. "Just had an amazing hour with my little man!! Smiles all round.. Have a great day everyone!!"

There is a reason why any of this is relevant, and it relates to the events that took place in London exactly five years ago. On September 12, 2005, The X Factor could go hang. Pietersen was too busy playing the innings by which his career is sure to be defined - that ludicrously cocksure 158 against Australia, through which England sealed the Ashes on the final day of the fifth Test at The Oval.

It was an unspeakably brilliant onslaught, and it changed Pietersen's life overnight. Less than 24 hours later he was parading through London on an open-top bus with his dead-skunk hairdo to the fore, more alert to the acclaim than any of his pie-eyed colleagues, and impatient for the start of a new life in the spotlight.

Five years down the line, however, the man who played that innings and soaked up the trappings of fame has to all intents and purposes vanished. Earlier this week Pietersen was back at The Oval, but in far less glamorous circumstances. Dropped by England for the first time in his career, following the longest and most troubling lean patch he's ever endured, he made scores of 0 and 1 on his Championship debut for Surrey, having signed off for the international summer with a horrid first-ball waft against Mohammad Amir at Lord's.

The accepted causes of Pietersen's slide towards mortality are well known. First there was the humiliation of his removal from the England captaincy - an accident waiting to happen, it was suggested, despite the fact that his reaction to the Mumbai bombings had, only weeks earlier, been lauded as "statesmanlike". Then there was the cruel timing of his Achilles injury and subsequent operation, through which he was robbed of a major role in a second Ashes triumph, and as a result of which he was left with far too much time to brood on his misfortune. His subsequent struggles in South Africa, during his maiden Test tour of the land of his birth, were indicative of a man with a muddled mindset.

And yet, there's more to his story than just a string of tough breaks, for Pietersen has been telegraphing his priorities in life for almost as long as he has been at the top of his game. In the summer of 2007, shortly after reaching his career-best 226 against West Indies, he warned that his burning ambition might not last for evermore. "There is a lot of cricket being played these days and time will tell how fatherhood changes my attitude," he said. "I know I don't like spending time away from my family. I don't like it at all."

That much was clear in the Caribbean last spring, where he notched up his most recent international century, but ended the tour declaring that he would never again go 11 weeks without seeing his wife, Jessica. His subsequent falling-out with Hampshire stemmed from a related issue - his desire to play for a county on his Chelsea doorstep rather than a three-hour round-trip away, to cut out commuting and cash in on family time.

All of which is laudable, but appears to drastically undermine the drive that once seemed set to propel Pietersen to the very pinnacle of the English game. "Everyone's game evolves," said Graham Gooch, England's batting guru, whom Pietersen has been working with on a one-to-one basis in a bid to rid his game of the blues. "KP has got to find the method that works for him at this moment in time. You might retain parts of the game you had before, but you have to upgrade and evolve."

Gooch knows that better than most, having twice undergone major technical surgery in the course of his 20-year international career - most notably in 1989 after Terry Alderman had laid him low in that summer's Ashes. But while Pietersen's problems against left-arm spin echo Gooch's swing-bowling Achilles heel, his most pressing challenge appears to be one of mindset. He's no longer in the zone, and subconsciously if nothing else, he's struggling to find the motivation to get back in there.

"KP is not a confident person," said his former captain Michael Vaughan. "He obviously has great belief in his ability but that's not quite the same thing." Five years ago, in a memorably gauche interview with the Wisden Cricketer, Pietersen blinked incredulously at his interrogator when she dared to ask him if he ever suffered doubts - nothing at that stage had come close to denting his monstrous and armour-plated ego. Now, however, he appears to have dropped his guard entirely. "I'm nowhere near the person I used to be," he conceded in an interview on the eve of the Lord's Test. "My confidence has taken a hammering in the last 18 months."

Notwithstanding his travails for Surrey against Glamorgan, the most recent hammer-blow came last week, when Pietersen was dropped by England for the first time. To the credit of the selectors, and in particular Andy Flower, there was no disguising the decision in weasel words such as "rested" or "rotation" either. It was a straightforward axing for a jaded and distracted player, and perhaps the jolt Pietersen needed to end the assumption, held by many in the media right up until the moment it happened, that he was undroppable.

And while the nature of Pietersen's "it's a f***-up" Tweet earned him a strong rebuke from the ECB, it probably also elicited a subtle sigh of relief as well. For whether it was intended for public consumption or, more likely, for the private eyes of Goughie or Vaughnie, the message showed a man who still cares deeply.

Professionally, Pietersen has not been this low since he first arrived at Cannock in Staffordshire in the summer of 2000, to set in motion his crazy bid for England recognition. Back then he was fuelled by a desire to prove himself to the world. The challenge he's now been set is to get off the sofa and do it all over again. Next month's stopover in Durban, where he'll face the demons that first drove him from his homeland, is as good a place as any to reignite those fires.