SONIA O'SULLIVAN's hopes of Olympic gold were in ruins last night after she sensationally ran off the track with 900 metres still to go in the final of the women's 5,000 metres championship.

O'Sullivan was at least 100 metres adrift of the eventual winner, Wang Junxia, when she suddenly veered to her right, at the top of the finish" straight, down a tunnel and out of the Olympic stadium.

The crowd held its breath in disbelief as the Irish woman, one of the celebrity athletes of the centennial games, ended the biggest disappointment of her career and wandered into the shadows to escape prying eyes.

There's no injury there I just had a word with her on the way in, she said she'd talk to me tomorrow. I just hope that she can pick things up for the 1,500 heats on Wednesday.

Once inside the mixed "zone, she broke down and wept. First she sought the sanctuary of her agent and friend, Kim McDonald, and then, when her father appeared, they hugged each other tenderly as the tears flowed.

The concern of John O'Sullivan was not for Olympic ambition gone wrong, but for a daughter who was in obvious distress. Many times he had embraced her in victory. Now he was at her side in the blackest minutes of a superb career.

Then she turned away from the press and, cloistered by her handlers, headed in the direction of the changing rooms. For once, there was no appetite among the media to take up the pursuit. There are occasions when intrusions into private grief are inexcusable and this was one of them. The story of her dramatic exit will rank as one of the great mysteries of these championships.

In two years, in which she was acclaimed champion first of Europe and then the world, she has only twice experienced the pain of defeat. On each of those occasions, she was close enough to the winner to retain her respectability.

No such solace was available last night after a weak, inept performance which a novice runner might have disowned. In hindsight, one can record the fact that she looked tense and unusually uncomfortable as she warmed up before the start.

On at least three occasions she turned and sprinted down the straight as the starter prepared to call them to the line. That was unusual for an athlete who has lived with the pressures of big time competition for the last six years.

It is possible, of course, that the burden of expectancy generated at home and over seas in the weeks and months leading up to the Games eventually got to her. Until such time as she speaks, it will be impossible to confirm the validity of that theory, but for the moment at least the nation can only wait and wonder.

Conditions were warm, but not oppressively humid, certainly not enough to distract the young British runner, Paula Radcliffe, who ran with commendable composure and courage to finish fifth. Even higher placed was the Italian, Roberta Brunet, an athlete who doesn't rate a place in the top 12 in Europe, but who still managed to take the bronze medal behind Wang and the young Kenyan, Pauline Konga.

If there is a logical explanation at this point it is that the opposition, conscious of O'Sullivan's status as an overwhelming favourite, set out to break her rhythm by injecting extra pace at different stages of the race. Not since Stuttgart in 1993 had she been asked to legislate for such a situation. However, the consequences last night were even more disastrous than they were on that occasion.

In one instance, at least, there was a common denominator in the fleet footed Chinese woman Wang. In Germany, with the cooperation of her team mates, she bemused O'Sullivan so deeply that she finished out of the medals in fourth place.

There were no Chinese colleagues on hand last night to assist Wang's plan of campaign, but the end product was just as decisive when, after loping along with the pack for the bulk of the race, she suddenly cut loose with a bewildering turn of pace with 800 metres to go.

For a woman who had run a tough 10,000 metres heat less than 24 hours earlier, it was a remarkable illustration of endurance running. Despite her eclipse in the world ratings in 1995, she now looked as unbeatable as ever. Strong and self assured, she was capable of finding an extra gear when the official demanded it.

On this display, few will bet against her completing an unprecedented double when she presents herself on the starting line to challenge for Derartu Tulu's 10,000 metres title on this track in the early hours of next Saturday morning.

O'Sullivan, meanwhile, has to ponder the prospect of returning to the scene of her torment for the heats of the 1,500 metres championship on Wednesday. Just how much this nightmare will affect the level of her competence is a matter for pure conjecture at the moment, but the certainty is that it will require a deep psychological exercise to enable her to recover from the 12 minutes of misery she was made to endure early this morning.

It was the Swedish runner, Sara Wedlund, who took the lead from the start, but as we were soon to discover, it would change hands with bewildering rapidity over the next 2,000 metres. By lap two, O'Sullivan may have already realised the name of the game when, after a surge to the front by Konga, she suddenly found herself relegated to eighth place.

By the end of the first 1,000 metres, reached in a modest 3:06.15, she was already lathered in perspiration and finding it difficult to keep a position in the heavy traffic.

She moved into second place on lap three, but then after New Zealander Anne Hare had taken over from Konga up front, she was once more swallowed up in the chasing pack.

There was perhaps the first significant indication of trouble on lap five when O'Sullivan, caught on the kerb, used her elbows and her strength to force a way through. That was untypical at such an early stage of the race and it portrayed, perhaps, the self doubt which may have begun to well up in her mind.

Significantly, it was when O'Sullivan was at the height of her troubles that Wang made her decisive burst to the head of the field. O'Sullivan, caught for speed, couldn't respond, and in a matter of no more than 50 metres she had drifted out of contention as a realistic contender.

Further and further, she receded through the pack until on the eighth of 12 laps, she found herself in 15th and last place, 45 metres off the pace.

From there on, one disaster superseded another for the favourite. The piston like drive left her legs, her mouth opened and suddenly her head began to roll in a manner which reflected her inner turmoil.

Then, dramatically, she was gone, as Wang decided that the time for real racing had arrived, and sprinted away from the abrasive Konga with two laps to go. From there on, the Chinese woman was on her own as she swept home in a time of 14:59.88, almost three seconds ahead of the Kenyan.

At that stage, the full extent of O'Sullivan's collapse was beginning to become apparent beneath the stand and one of the great talking points of these centennial Games was already up and running.