After 10 years away from tennis, Bjorn Borg returned in 1991, unfit and still using a wooden racket. He was humiliated. Now, after years of troubles, the reclusive Swede tells Tim Adams just why he made his ill-fated comeback

23 April 1991, The Monte Carlo Open

For a very long time Bjorn Borg looked like a man far more likely to break others' hearts than to have his own heart broken. Few sportsmen have been as merciless as the Swede. The late Vitas Gerulaitis, his great friend, once recalled of their matches: 'Every time I play Borg I come out with some 30 ideas that should get me victory. And each time Bjorn breaks each one of the 30 to pieces, like a clay-pigeon shooter.' They practised together most weeks on tour and played each other 16 times in tournaments, including an epic Wimbledon semi-final in 1977. Gerulaitis never won once. Every player Borg faced had a similar story. Jimmy Connors, the greatest slugging competitor, lost 10 matches in a row to him. Ilie Nastase, the master gamesman, was brutally denied the Wimbledon championship he felt was his destiny by the 20-year-old Borg in 1976.

For his six consecutive French Open titles and five Wimbledons, unparalleled summers of achievement, it seemed that failure would never be an option for Borg. His arrival in SW19 in 1973 had been heralded by the hormonal screams of girl fans, a new sound on Centre Court; but by the time he won there three years later, even those screams had faded. There seemed no way to get to him, so focused was he on the next ball, and the next.

In this pursuit of perfection, nothing was ever left to chance - Borg's Wimbledon routine was the same every year: the same hotel in Hampstead, the same locker, the same chair, the same number of towels on Centre Court. The same abstinence from shaving and sex for the duration of the tournament. And the same result. Everything beyond that, Borg had removed from his game by drills and application. There was no excess flourish about his strokes, no recrimination when he mishit, no emotion beyond absolute determination. His heart, which pulsed extraordinarily slowly at 29 beats a minute, never once, it seemed, came into it. Because he was mostly spared the drama of defeat, his victories sometimes lacked romance. And his retirement at 26 seemed to be born of a typical cold-blooded logic.

In 1981 Borg had lost, twice, to John McEnroe, the first and only player to get his number, at the final of Wimbledon and at the US Open. After the latter defeat, Borg walked off court and out of the stadium before the ceremonies and press conference had begun; he went straight to the airport and never looked back. Borg had no interest in being the number two player in the world, it seemed. It was number one, or it was nothing. He had had his time. He knew to quit at the very top, without putting himself through every great champion's story of dwindling expectation. He would not expose himself to that humiliation: the prodigy's knowledge that even he would have to grow old.

Oddly, it was only when he stopped playing that Borg seemed to become fully, frailly human. The headlines he had made as a player of adamantine resolve were replaced by tales of bankruptcy and disastrous relationships. His first marriage, to the tennis player Mariana Simionescu, failed when he met a 17-year-old while judging a wet T-shirt competition and fathered her child. He then married, briefly, the Italian singer and one-time glamour model Loredana Berte. By the time that marriage was almost over and his clothing business was foundering amid lawsuits and lost fortunes, Borg looked a lot different to the peerless King of Wimbledon he had been. It was then, at 34, that he decided to make the most poignant of comebacks at the high-profile clay-court tournament in Monte Carlo, by then his home town.

Time, in sport, moves extremely quickly. Borg, stubborn as ever, appeared to want to ignore that fact entirely. He made his return with his antique small-headed wooden racket - when all around him were wielding great graphite clubs - wearing the same brief Fila kit that he had made his trademark. He lost to Jordi Arrese, a journeyman Spaniard, in straight sets. A couple of other similar defeats and the cringe-inducing return was over.

Talking to Borg now, in Birmingham, in a rare interview on the day after he has won the BBC Sports Personality lifetime achievement award, he is happy to laugh a little at the hubris and embarrassment of that attempted comeback. 'You know,' he says, 'the thing was I just wanted to play tennis again. After I retired I did not play much for seven or eight years. In 1991, I decided to come to play Monte Carlo. It was a big tournament. I was living in Monte Carlo. I played no practice, no exhibitions, I just kind of turned up.'

The most exactingly prepared man ever to hold a tennis racket, wanted, it appeared, to find out if he could do it without trying. 'It was madness; I knew that,' he says. 'I knew I was not playing well. But I can't explain it except to say I wanted to play. One or two years later Jimmy Connors started the senior circuit. If they'd had that in '91, I would have done that instead. As it was, I went to Monte Carlo.'

And the wooden racket?

'Well, I had never played with anything else. I knew that if I wanted to do well I had to use another racket but I thought, you know: why change?'

He would never say as much, would not allow himself that much psychology, but there was something about that heartbreaking comeback that went far beyond a simple desire to play. It looked a lot like Borg laying ghosts to rest, a slaying of his own legend. This, he seemed to be saying, is why I stopped, because no one can do it for ever, win for ever, life is not like that. What he proved, when he came out those few times in his thirties, was not only that he was big enough to lose; but that winning was not the only thing. It has been claimed that the comeback destroyed Borg's cool mystique; on the contrary it seems to me that it reaffirmed it - it showed, after all those years, just how much, underneath it all, that the game meant to him.

Now aged 50, Borg is in relaxed good health. He has stayed on in Birmingham to launch his range of underwear at the space-age Selfridges store, so he is surrounded by teenage models in boxer shorts. He seems quietly amused by his life and unusually happy to talk. For a long while after he finished the game it was not like that for him, however. He had his own mythical past to contend with and it was a hard reputation to bear, a kind of stoic genius that was at odds with the new reality of his life.

'When I played tennis up to 25 everyone could only see the positive things about me, really,' he suggests. 'Afterwards, if I did something negative, they always measured it against what I had done before. To be so perfect in my tennis, and as a person in some ways while I was playing, that was always going to be a hard act to follow.' Monte Carlo was one way of coping with that, his way of reminding himself and everyone else that he was vulnerable, that he could make mistakes.

Oddly, he says, the moment that vulnerability first hit him with proper force was also the moment of his most famous triumph. It came at the end of his tie-break with McEnroe in the Wimbledon final of 1980 when, having surrendered seven match points, he walked back to his chair with the final all square at two sets apiece. That was the first time, he says, in all of his winning years at Wimbledon, that he entertained the thing he most feared: doubt. It was the first time he ever really believed that he would lose. He had never watched the final again, never seen the point of that, until recently, when his children forced him to sit down with them and talk them through it.

I wonder how it feels to him, seeing all that tension after all these years. Watching that other life?

'Well,' he says, laughing, 'it helps that I know the result. But watching myself losing that last point, 18-16, I can feel that walk back to the chair now as if it was yesterday. That was the toughest moment in my tennis career, that walk. I knew John thought he would win the match. I thought he would win the match. I don't know how I regrouped. If he had broken me in the first game of the fifth set I would have lost, but I won from love-30 and then I played just unbelievably well, hardly lost a point on serve and won the match. That was the strongest set, mentally, in my tennis career.' But it was also, he had recognised, the beginning of the end.

The strangest thing, he suggests, was that of all the Wimbledon finals the one he should have won most easily was the one he lost, in 1981, against McEnroe. 'I felt I was much the better player that day. But I just wasn't so focused. And when I lost what shocked me was I wasn't even upset. That was not me: losing a Wimbledon final and not upset. I hate to lose. It was the same at the US Open. Losing to John again I was relieved the match was over.' He knew that something had gone for good and, despite McEnroe's desperate efforts to persuade him not to retire, to continue their rivalry, he knew he would not properly get that thing - desire - back.

'The difficulty is,' he says, 'when you play at that level you don't have problems. If someone had said to me while I was playing tennis, "Look, I have this problem in my life", I would not have known what they meant, not really. Everything was looked after for me. I was following my schedule. Practice, eating, sleeping...' He craved, I suppose, complication, disorder, indiscipline (you might say he wanted to be John McEnroe). Once he stepped out of the lines of the tennis court, he found them.

'It took many years to find peace with myself and to find what I really wanted to do,' he says. 'I had a lot of choice, a lot of opportunities. I tried lots of things, some good, some bad. It has taken me this many years to get to where I want to be.'

I wonder what he looks back on now - from the vantage of an idyllic home life in Stockholm, a young family - as the lowest points. There were, around the time of his comeback, rumours of a drug overdose, a suicide attempt?

He denies this strongly, suggesting that the rumours grew out of an admission to hospital with food poisoning. But still around that time, with the collapse of his business interests, he acknowledges he felt under severe strain. 'Money is important, but not that important,' he says. 'The most disappointing thing was that people abused me, you know. When the business started, I thought these people were my friends. But they were all out to screw me really.'

One of the things that has allowed him to rebuild his life is the renaissance of his clothing line, its retro look inspired a little by the playboy image of tennis in the 1970s (one memorable advert for his briefs implored Swedes to address urgently the falling birthrate: 'Fuck for the future' ran the strapline). The invocation worked, apparently; Bjorn Borg is second only to Calvin Klein back home. 'We are now doing unbelievably well,' he says. 'New designers, new managers. We are on the stock market in Sweden, in 10 different territories in Europe and the business is huge ...'

I wonder, despite this success, if it still hasn't, in the underwear business, been impossible for him to recreate the intensity of his tennis years.

'The intensity is not the problem,' he says. 'One thing is, as a man, you have to find a great woman. Unfortunately this is the third time I got married. That is nothing you aim for. Hopefully you want to stay with the same woman. But if you are not peaceful with yourself, marriage is not going to work.'

His current contentment explains his apparent reclusiveness in recent years he says. He and his wife, Patricia, have a son of three, as well as two children from her previous marriage. They live outside Stockholm on an island in the archipelago. He gets up with the kids at six, plays tennis five times a week and coaches Swedish juniors.

Like McEnroe, he has never lost his love of the game whether playing or watching. Lately, he says, he has become friendly with Roger Federer. He practised with him recently in Dubai and he can't help but see a lot of himself in the four-time Wimbledon champion - and also a lot of his rivalry with McEnroe in Federer's matches with Rafael Nadal.

I wonder if he can immediately recognise in any young pretender the potential not just to reach the top 10, but to be the best?

'I think so,' he says. 'After Federer, I think Andy Murray has a great chance to be the next number-one player in the world. He has the heart for it. You can always see straight away the people that will put themselves out there. Henman had it, too, actually. He never made it, but at Wimbledon in particular he gave himself chances.'

Last year, there was a surprising story involving Borg's plans to put up his Wimbledon trophies for auction at Bonhams in London. At the time it seemed like this was to solve a financial crisis, but that did not square with the success of his business, and he denies it now. 'It wasn't a money thing, not at all,' he says. 'Over the years I have been giving away trophies to charities, for kids tournaments. I have given away everything, all my kit, shoes, lots of trophies. The only things I had left were the Wimbledon trophies, my French trophies, and the Davis Cup medals. And I wondered if, at 50, I should sell them. Because no one can take away my memories of these things, of Wimbledon, they are always there.'

He was hugely surprised by the reaction. 'I had no idea,' he says, 'the fuss it would cause. People all over the world contacted radio, television. They all said you cannot sell your trophies. We have lived this with you, you can't just give it away.'

Borg was uncertain. Then the other person to whom the trophies meant most called. And called again. 'McEnroe called me many times, saying, "What the hell are you doing?" ' he recalls. Except you imagine he did not quite say 'hell'. In the old days, perhaps, Borg would not have listened to his friend. But he has learned a few things over the years and one of them is that it is not worth arguing with McEnroe, life is too short. 'I bought them back off Bonhams,' Borg says smiling, 'and they are in a safe place. They are only trophies, but I will keep them now for ever.'

· Tim Adams is the author of Being John McEnroe (Yellow Jersey)