On the first day of school, all the girls were proud of their new uniforms. In their smart, neatly pressed yellow blouses and red dresses, they stepped through the rubbish-strewn alleys of an African township and made their way to report for their high school education.
Like young girls the world over, the new pupils chatted and laughed as they made their way to class, sniggering and nudging each other when they walked past groups of boy students. But one girl did not share this liking for dresses, giggling and gossip.
Already tall and brawny at 11-years-old, with a strangely gruff voice, this student did not stand out simply on account of her striking physique.
Happier days: Caster, left, with pals Debbie Morolong, right, and Ilanda Mongala
No, what really set her apart from her fellow female pupils was the fact that she always preferred to dress as a boy.
Amid sniping from fellow pupils, she wore long grey trousers and a boy's shirt from the day she started school near Seshego, a township in South Africa's remote Limpopo Province, which butts against the borders of Zimbabwe and Botswana.
That is not all. This girl student was also 'rough' and preferred playing - and fighting - with boys. Indeed, even as a baby, she had kept clear of any 'girly games' such as dolls or dressing up.
Instead, she liked football, karate, wrestling and rough and tumble with other male school friends. She was also big enough and tough enough to ensure nobody criticised these activities to her face.
The name of this unusual student? Step forward Caster Semenya, 18-year-old from an impoverished black township who is at the centre of a row raging across the world following allegations that she is, in fact, a man.
In a week that has seen astonishing sporting feats being achieved at the world athletics championships in Berlin, one of the most eye-catching was the surge to glory by Semanya, who set new records in the 800 metres after leaving her opponents floundering far behind in her wake.
Evidence: Caster's birth certificate
Her family and friends crowded into a shack with a corrugated iron roof to watch the race on an old television.
In many ways, with her boyish running shorts and powerful, flat chest, Caster looked like a young Usain Bolt, the Jamaican sprinter who broke his own world record as the fastest man on earth and then clocked a stunning 200m world record.
And that suspicion proved to be her curse, prompting a row that has forced the world's athletics authorities to subject her to a gender verification test, while the controversy has led a huge debate involving gynaecologists and race relations experts.
The question everyone wants to know is: can Caster Semenya really be all woman, looking the way she does?
While her family cheered her victory, an Australian sports official commented crudely: 'There's something dangling between her legs - that's obvious - and she's got an Adam's apple.'
This weekend, as Caster remains in hiding, athletics chiefs are preparing to carry out these humiliating gender tests which will include an external and internal examination which will look at her reproductive system and chromosome make-up.
So what is the truth about Caster Semenya? What's more, will her fragile teenage psyche ever recover from the damning remarks about her looks?
One man who knows the answers is Caster's father. A gardener for the local council in Polokwane, formerly Pietersburg, he is a shy, private man.
But as night fell last night, he sipped on a Coke and spoke for the first time in depth about the strange little girl he fathered - who has never worn a dress in her life.
Jacob Semenya's life has been turned upside down in the few days since his fourth daughter discovered that, if she has too many male characteristics, she will be stripped of the gold medal she won in Berlin and return home under a cloud of shame.
'From the time she could walk, Caster only wanted to play with boys,' he said, smiling ruefully. 'Her three elder sisters wore dresses, as little girls do, but Caster refused. She has never had a skirt, only trousers.
'I knew she was different to the others, and even now if you speak to her on the telephone you might mistake her for a man. But I used to change her nappy, and I know she's a woman. What better proof do people need?'
Caster and her friend Debbie Morolong. Caster always preferred to dress as a boy and kept clear of any girly games
He cheered after her gold medal victory but felt physically sick when the news came through that she was to have the gender tests.
'I don't even know how they do this gender testing,' he says. 'I don't know what a chromosome is. This is all very painful for us, we live by simple rules in our culture. We do not intrude. This is not natural. To go through such an unusual thing must be very hard for Caster. I really have been concerned for her well-being.'
However, Caster phoned home from Germany and was very stoical about her plight. 'She told me not to worry. She said: "Dad you know me, I'll be fine. I'm not fussed.'' '
Like countless South African men, Jacob Semenya works and lives away from home, returning to his family only once a month to give them his wages. Caster and the rest of his children grew up in the village of Fairlie, deep in South Africa's northern Limpopo province.
Built on a remote African plain and accessed by a single dirt road, most people work as farmers and labourers. The Zion Christian Church dominated life for Caster, her mother Dorcus Semenya, her three sisters and brother.
When Semenya was born in 1991, her father was so determined to earn enough to look after her that he worked away from home for weeks. With three daughters, Jacob had desperately wanted a son.
He got a girl - albeit one with many of the characteristics of a boy. 'When I was told it was a girl, I did not mind. I was just very proud to have another child. I was not allowed to check the baby's gender for myself. That's the job of the elderly women, who then make a pronouncement.
'In our culture, the father is not allowed to even touch his baby until the umbilical cord has fallen off. Then the old women of the village take it away and the man is handed his child. This week, I thought of how tiny she once was. I still feel very protective of her.'
Caster grew quickly, becoming taller and more thickset than her friends even as a toddler. 'She was always running around, even as a little girl. She was preoccupied with sport - she never played with dolls. She was a good deal bigger than the other schoolgirls.'
Caster has a strong, muscle-bound build which made her good at athletics at school. She is pictured here last year during schools athletics
She hated the romantic films loved by her sisters - and used to fight with them because she wanted to watch old wrestling and karate highlights. She spent the rest of her time playing football with her male cousins.
But her powerful physique quickly started to cause problems. She was disqualified from playing women's football by the age of 14 - the coaches said she was too rough with the other girls.
'She was heartbroken,' says her father. 'Up until that point, Caster had lived for football and she was desperate to play the game. The coaches said she was a "hard mama" - too tough and too big to play.
They disqualified her from the women's team and she couldn't play with the men, so her career was over. She was upset, but didn't cry.'
Nor, as a young was she interested in the other obsession of her fellow female pupils: boys. 'Caster has never cared about men other than as friends,' says her father.
'Her sisters were always after boys in the way that I, too, was always after girls when I was younger. But Caster has never been interested in any of that.'
Instead, months after being drummed out of the football team, she discovered a new passion for running and began training after school under the tutelage of her headmaster, Eric Modiba, who says he initially thought Caster was a boy. 'She was always rough and played with the boys,' he said last night.
'She liked soccer and she wore trousers to school. She never wore a dress. It was only in Grade 11 that I realised she was a girl.'
Her few female friends also noticed that Caster was not like them. 'She never had a boyfriend,' says Deborah Morolong, Caster's best childhood friend. 'She doesn't like boys. But that doesn't mean she is not a girl.'
In an attempt to end the controversy about her gender status, her family yesterday showed a copy of Caster's birth certificate. It backs what her friends, family and teachers insist is the case: that the 18-year-old is a woman, albeit clearly with some male characteristics.
The certificate confirms her birth date as January 7, 1991 and clearly states 'female' under the section marked 'gender'. Written in Afrikaans and English, the one-page birth certificate includes Semenya's full name, Mokgadi Caster Semenya. The document also lists her ID number and confirms her country of birth as South Africa.
Semenya's sister Nkele, 16, said: 'This is proof that my sister is a girl. She was a girl when she was born and she is a girl still. Hopefully this will stop people making rumours about her.' Of course, these rumours have dogged Caster's athletics career - and the birth certificate had to be produced on numerous occasions to assuage the doubts of other female competitors. 'More often than not, when we met other schools for athletics there would be some question about Caster's gender,' said one school official. 'We took to keeping a copy of her certificate so we could show beyond doubt that she is a female.'
Fellow teacher Moloko Rapetsoa said: 'Some schools, suspecting that she was not a girl, even demanded that her status be checked. But each time they returned from the toilet, she would be cleared and the competition would resume.
'We would ask her why they had taken her to the toilet, and she would just say: "They are doubting me", without explaining further.'
It seems unlikely that so many people could lie about Caster Semenya's sex. Now, medical experts are speculating that she may be a quirk of nature - a woman with either under-developed male sexual organs inside her body, or an abnormal number of male chromosomes.
There is also, of course, speculation that her sudden improvements in running times and classically male physique suggests she has been using performance-enhancing drugs - which raise testosterone levels and can lead to male characteristics developing in women.
For all her talk of her 'toughness' and thick skin, it emerged last night that this young girl from rural Africa has been deeply hurt by all the comments about her looks. Indeed, it emerged that she had considered boycotting the medal awards ceremony after her 800 metres triumph.
She was so angry that one of her coaches needed to persuade her to go to the podium to collect her prize 'No one ever said I was not a girl, but here [in Berlin] I am not,' she told friends. 'I am not a boy. Why did you bring me here? You should have left me in my village at home.'