The hints were there in her behaviour at the French Open earlier this month. In the final of the women's singles against Steffi Graf, Martina Hingis transmogrified from the brightest, cheeriest, sanest of tennis prodigies - a woman whose equanimity and good grace charmed everyone who met her - into a spitting, cursing, bawling amalgam of John McEnroe and Ilie Nastase in a skirt and frilly knickers. She behaved appallingly, served underarm in the final furlong of defeat, skulked away without so much as a congratulatory handshake for her opponent and had to be coaxed back on to court for the prize-giving formalities by her mother. But a week later, refreshed by a short break in her native Slovakia riding horses, Hingis claimed to have put the incident behind her. "I'm still young and I hope I can learn from this," she said jauntily, as she prepared for Wimbledon without a hint of contrition. "I will do, otherwise I'm not going to get anywhere."
Last Tuesday, after defeat at the first hurdle at Wimbledon, a completely out-of-sorts Hingis proved she was still on the lower slopes of the learning curve. At the press conference, seeking to explain the defeat by the qualifier Jelena Dokic, she spluttered about the pressure of the tennis circuit being all too much for her. But before Hingis is dismissed as an over-emotional, overwrought, over-paid woman too spoilt to accept defeat with any measure of good grace, it is worth pointing out one thing: she is 18. An astonishing thought that. While the greatest achievement of most of her contemporaries is to have just completed their A-levels, she has already won five Grand Slam tournaments, popping a total of £10,085,496 into her kit bag.
All her teenage life, she has lived with the kind of pressure of expectation and desire which few of us will ever experience even as adults. The only surprise, when you consider her predecessors as tennis prodigies, is that Martina Hingis has lasted so long without any sign of emotional subsidence. Remember Tracey Austin, who won the US Open twice before she was 17? Or Andrea Jaeger, who packed in the game completely at 16 and now runs a foundation for handicapped children? Or Jennifer Capriati, who escaped teenage tennis into a world of drugs and counter-culture before returning to Wimbledon on Monday night looking older and wiser. None of them was exactly noted for the longevity of their careers. And what did all of those prodigies, who in their different ways have cracked under the searing pressure of the circuit, have in common? Pushy parents. It is now a central paradox of success at tennis that you require the very thing in a parent which may well inflict long-term psychological damage. To succeed at the game, you need to be picked up young and trained hard and competitively from the age of six; by eight, you need to be under specialist coaching supervision, by 10 you need to be forgetting all other interests in life. Completely. The only way that can be achieved is under the influence of a parent not so much supportive as desperate: Hingis's mother, Melanie Molitor, was coaching her seriously from the age of two.
"I'm not sure why people always regard this as something unnatural," says Mitch Fenner, of the University of Wales Sports Science department and a former international gymnastics coach. "After all, no one seems to sneer at people encouraging their children to become musical or maths prodigies. It requires the same dedication." For girls, the pressure starts even earlier than for boys, simply because to succeed in the sports at which women excel - tennis, swimming, gymnastics - a performer has to reach her peak at a younger age than her male counterpart. So even though Andre Agassi and Pete Sampras had impatient dads, they had to hold back until adolescence was over and their boys' bodies had achieved the physical strength required to succeed at sport. For girls there is a major advantage in peaking before puberty plumps out the physique and slows the responses.
"Female competitors certainly experience pressure earlier in life," says sports psychologist Gordon Baxter. "And it is often added to because they have such intense relationships with their parents, who often double up as their coach." Children can never escape the pressure, never regard their parent as anything other than part of the relentless grind. As poor Mary Pierce, Steffi Graf and the Williams sisters - Venus and Serena - have discovered.
Yet ambitious parents are ever more reluctant to hand over responsibility for their girls' sporting development to outsiders, and ever more willing to take the DIY route and relinquish all other aspects of parenting. "It's a sad but documented fact of life," says Baxter, "that several coaches have abused the particularly intense relationship they form with young girls."
Add to that the extra burdens from sponsors of competitors such as Hingis and Anna Kournikova, the Russian currently starring on a computer screen saver near you. Kournikova recently signed a deal worth several million pounds to promote Berlei sports bras. No wonder she double faults so often - she must be wondering as she addresses the ball, what all those physical jerks associated with serving are doing to her chest.
Oddly, though, Hingis always seemed to have a more mature relationship with her pushy parent, not least because it was her mother doing the pushing. Generally reckoned to be inclined towards the liberal wing of pushiness, Melanie Molitor has always encouraged her daughter to have some sort of hinterland outside the game, hence the horse-riding. But these things are relative: Molitor was never inclined to let her daughter relax. Unusually, it may well have been Molitor's absence at Wimbledon which cost her daughter her chance of winning another Grand Slam, not to mention retaining her composure. "We have just decided to have a little distance and probably work on our private lives a little more," blubbed Hingis after defeat on Tuesday, a defeat which granted her a fortnight longer to work on that privacy than she might otherwise have wished.