As the whistle blew at the conclusion of England's victory over France in the semi-final of the 2003 World Cup, the triumphant team erupted in celebration. All except one player. Jonny Wilkinson, the side's talisman, who had scored all England's points in the match, commiserated with his opponents and then jogged from the pitch, head bowed. He had no inclination to engage in celebration or high fives. His complex mind was already gripped with the familiar feelings of fear and insecurity as he turned his attention to the final seven days hence.

This is Wilkinson as he once was. Wilkinson the fabled monomaniac. Wilkinson the obsessive, who would spend five hours each day engaged in kicking practice and then spend the next five hours beating himself up about the one he missed. Wilkinson the troubled loner, never able to free himself from the exhausting and seemingly futile quest for perfection.

“I did not know what it really meant to be happy,” he says when we meet at Kingston Park Rugby Stadium, Newcastle, his long, golden locks hinting at the dramatic transformation he has undergone in recent months. “I was afflicted by a powerful fear of failure and did not know how to free myself from it. I would be watching a movie with friends and everyone else would be absorbed in the plot but I would be looking at the frame of the television, my mind on what had gone wrong in the last practice session or what I would be working on in the next. Someone would see my eyes wandering and ask if things were all right and I would say ‘yes'. But they weren't.”

A week after the defeat of France, Wilkinson executed the iconic dropped goal that secured World Cup victory for England over Australia. It was a moment of supreme vindication, the day to which he had been building since he first wandered on to a rugby pitch (at the age of 5). And yet within 24 hours he was hit by an overwhelming, almost concussive sense of anticlimax. As he says in his new book, Tackling Life: “I felt like I was tumbling out of control.”

But things were about to get much worse. Between 2003 and 2007 Wilkinson endured a series of injuries that prevented him from playing a single match for England and limited his club involvement to sporadic appearances. For a young man whose world revolved around rugby, and whose fragile self-esteem was bound up with his performances, it was a living nightmare. He tried learning the guitar and the piano, then French and Spanish - anything to release his highly active mind from a growing sense of despair. Thankfully for Wilkinson, salvation was just around the corner. Deprived of the thing that had given his life meaning, he began to look elsewhere, reading everything he could get his hands on. But it was not until he stumbled across quantum physics that he experienced the epiphany that has transformed him into the relaxed, smiling, warm, discursive and deeply spiritual person sitting alongside me. “I read about Schrödinger's Cat [a renowned thought experiment in physics] and it had a huge effect on me,” he says. “It was all about the idea that an observer can change the world just by looking at something; the idea that mind and reality are somehow interconnected. It is difficult to put into words, but it hit me like a steam train.”

For a sportsman to find enlightenment in the mysteries of subatomic physics is surprising enough, but Schrödinger's Cat was just the start of Wilkinson's spiritual odyssey. “I came to understand that I had been living a life in which I barely featured,” he says. “I had spent my time immersed in the fear of not achieving my goals and then spent my time beating myself up about the mistakes I made along the way. Quantum physics helped me to realise that I was creating this destructive reality and that all I needed to do to change it was to change the way I chose to perceive the world.

“I do not like religious labels, but there is a connection between quantum physics and Buddhism, which I was also getting into. Failing at something is one thing, but Buddhism tells us that it is up to us how we interpret that failure. The so-called Middle Way is about seeing everything as interconnected: success and failure, victory and defeat. Who is to say that the foundations of success in the 2003 World Cup were not built on the failures that went before? The Middle Way is also about having the right intentions. Are they decent and honest and are you giving consideration to other people? Selfishness can never be the route to happiness or success.”

Wilkinson has long been considered a deep and complex person, but perhaps the most striking thing about this new incarnation is his moral seriousness. That and his handsomeness. His eyes widen with earnestness as he expounds his philosophy and his surprisingly delicate hands tremble ever so slightly. His rugged features cut a profound contrast with the femininity of his personality, while his long locks - “the new hairstyle representing the new me, but don't assume I have gone back to my old ways if I decide to cut it” - add to a sense of mystique. I decide against telling him he is one of the most beautiful people I have seen, fearing it might interrupt his flow.

“The first draft of my new book [serialised in The Times tomorrow and on Monday] was packed with physics and spiritualism,” he says. “But I decided to take that stuff out because I thought it might confuse people - they might have thought I was trying to be the next Stephen Hawking [laughing]. Instead I have examined how my new attitude has changed the way I live my life and put that out there as an example others might learn from. I wrote it myself, longhand, and have spent a lot of time agonising over my choice of words because I don't want there to be any ambiguity in meaning.”

So you are still a bit of a perfectionist? “Yes, enormously so,” he says. “But this journey has been about learning to find the switch to turn it on and off when I need to. My obsessiveness is, in some ways, one of my greatest strengths: the ability to stay out there practising until things are right. But it's not a good thing if you don't have control of it. Now I can step back after a practice session and say: are you sure you want to do some more? Even if things have not gone perfectly I have the ability to flick the switch and go home and enjoy my weekend.”

This must have made you an easier person to live with. How has your girlfriend reacted to the new you? “It is interesting you should ask me that because before when journalists quizzed me on my personal life I would clam up,” he says. “But now I find

I can talk about it, because I am no longer so anxious about how things might be taken. To answer your question, my girlfriend [Shelley Jenkins, with whom Wilkinson lives and has been with for the past three years] is really happy for me. I have improved as a person in my relationships, not just with her but with friends and family. They can see I am much more at ease with myself.”

The question in the minds of rugby fans - both Newcastle and England - will be whether the philosophical transformation in Wilkinson is likely to impact negatively upon his effectiveness as a player. Judging by his performance for Newcastle against Northampton last Sunday, they have little to fear. Coming back after four months out with a shoulder injury, Wilkinson scored 22 points and made the scoring pass to create one of his team's two tries. But the icing on the cake was the last of his two kicks, an audaciously conceived and immaculately executed 45-yard right-footed dropped goal to settle the result. “I was not sure about it,” he said after the match. “I looked at the opportunity and thought that if it went over, great it would be the end of the game; if not, I would be giving Northampton, who were running riot at the time, another opportunity to attack. The new me needs to take these risks.”

It seems Wilkinson has unlocked a more relaxed, more audacious and, perhaps, more effective performer. The test will be in the autumn internationals when he is likely to feature for England with Danny Cipriani, his youthful rival for the No 10 jersey, out with injury. I ask Wilkinson if, in his new enlightened state, he has managed to uncover the reasons for the fear of failure that used to haunt him.

“I think it was rooted in an even deeper fear of death,” he says. “I couldn't figure out how to avoid death: it was like a game I could not win. The closer I got to family and friends and the better things got, the more I had to lose. But my faith has given me a handle on it, based around the ideas of rebirth and karma. It has also given me the ability to understand that rugby, like life, will also come to an end. I guess I had been trying to block that out, hoping that it would last for ever. But I have accepted my career will finish one day and I am in a place that will enable me to make that transition comfortably. I will not have to reinvent myself to cope with life after rugby.

“My motivation today has nothing to do with status, money or ego. Before I wanted to be the best in the world and I would watch other players to see how I measured up. Now when I do something great on the rugby pitch it is not about being better than others but about exploring my talent. I look around at the spectators and their enjoyment at having seen a great game. I reflect on the fact that my club, Newcastle, has become stronger, something that is good for the health of the business and the staff. My fulfilment is no longer about self-gratification; it is about seeing the happiness of others.”

Schrödinger's Cat ... What it told Jonny about himself

No one really understands quantum mechanics, we just know that it works because the mathematics and experiments support it. Of all its seemingly preposterous predictions, perhaps the strangest is that a particle is not in one place. It is in a series of places at the same time, defined by probabilities. But when you observe particles, they are definitely in one place. One way of resolving this is to posit that the very act of observing gives position.

To illustrate how this produces paradoxes, Erwin Schrödinger, the Nobel prize-winning physicist, imagined a cat in a sealed box. Inside the box is a radioactive source, a Geiger counter and a vial of poison. If the Geiger counter detects a particle, it releases the poison. Imagine there is a 50 per cent probability of the source releasing a particle in an hour, after which the box is opened. Until the source is observed, it has both released and not released a particle. So the cat, whose fate is linked to the source, must be simultaneously alive and dead. So that's cleared that one up.
TOM WHIPPLE

Tackling Life by Jonny Wilkinson with Steve Black is published by Headline on October 2 at £18.99. It is available from Times BooksFirst for £17.09, free p&p, 0870 1608080 timesonline.co.uk/booksfirst