Conceived in an environment literally swimming in synthetic oestrogens, Tessa had been unique, even amongst the thousands of children born into the twilight light zone between male and female. The reason had been deceptively simple: by the time she'd turned six, Tess had voiced her desire to be a girl. In effect, she wanted the right to choose her own gender. While Tessa's story hadn't made the front page of Time, it had caused a small hurricane of controversy amongst the pediatric specialists handling her case.

They'd wanted to flood her system with steroids before she entered puberty, adamant that this was the most logical course of treatment: he was a boy, he'd been born with a male organ (tiny though it was), biology dictated that he had follow his chromosomatic destiny. Tessa's wishes were, of course, completely irrelevant, he was a child, he had no idea what he wanted, and certainly, no concept of what was in his best interests.

This was precisely how they'd talked; emphasis on the masculine pronouns. They'd rambled on in this manner for some time, employing the authoritative, slightly patronizing tones that medical professionals retained for the ignorant: yes, his reproductive organs were completely atrophied: they'd never secrete the androgens he'd need to achieve manhood. But while he was incapable of producing his own testosterone, small daily dosages of the male hormone would ensure that he'd progress as God and nature intended.

He had to become a man.

Tessa's mother - Eva Greenhart, PhD - had been thoroughly unconvinced by these arguments. She'd read enough constructionist theory to know that a child's gender was not automatically determined by her sex. Gender was simply the product of culture and socialization, not an immutable law of physics dictated by anatomy and chromosomes.

Besides, why was masculinity considered the only option in this (or any other) case? Was femininity so undesirable? If they could change Tess into a man by boosting his testosterone levels, couldn't they just as simply employ oestrogen to transform her into a woman?

The endocrinal team had found the suggestion laughable (if not down right criminal) in its naïveté: synthetic oestrogens were the cause of Tessa's condition; by what stretch of the imagination did she conclude that the female hormone could be used to treat the boy's pathology? It's time you faced reality, Ms Greenhart: your son is suffering from an illness; his development has been arrested by foreign agents, his DNA damaged by toxic chemicals. From a medical perspective, he's no different from a victim of heavy metal poisoning.

Basking in the pompous, lilac glow of utter contempt, Eva listened in patient, nodding silence as they dictated her child's future, dismissing her (Tessa's) childish aspirations as totally unimportant. One of them had actually said that in his 'sexually unresolved' state, Tessa was no better than a neutered dog. Putting him on oestrogens would produce a sexual anomaly, a mutant neither male nor female, shunted to the periphery of 'normal' human society. Is that how you want your son to go through life? Are those the only choices you're willing to offer him:

Eunuch or freak?

And it had been this one statement, delivered in the offhand tones of complete insensitivity, which had made up Eva Greenhart's mind regarding Tessa's 'treatment'.

Ten minutes later Tessa was standing on the set with her face flushed the colour of a ripe strawberry. The only girl in the cast to be stripped to her bra and panties, she felt wonderfully vulnerable – her tiny lace remnants covered so little that she felt almost completely naked. The other girls milled around in their minnies and high heels, listening to the director's opening spiel.

Exhibiting a subtle pink flush from ankle to hairline, she crossed her hands over her pink satin wonderbra in a vain attempt to hide her deep cleavage. It was an impulse she was totally incapable of resisting: the director, the floor manager and most of the technical crew were men. Worse still, the set didn't appear to be closed; people seemed to be wandering in all the time, and she had immediately become the focus of all the attention of the masculine quarter.

She was almost swooning with pleasure.

It was strange: she had dreamed of this moment for years; since early high school in fact, but now that she was actually facing a battery of video cameras with her underwear on full display, her embarrassment was almost as vast as her delight. She'd never imagined how much she could actually enjoy being a public spectacle.

Anticipation washed over her in a warm, pulsing cascade. Her tummy was tingling with suspense; anytime now, the cameras would start rolling (or blinking or whatever it was that videocams do) and she'd be told to take her position for the first take. She was being overwhelmed with feelings and sensations, almost all of them drawn directly from childhood experience. This was hardly surprising in itself; she'd been only twelve years old when she had discovered that delicious blend of joy and humiliation which accompanies public exposure.

It had taken place during her first year of junior high school; she'd been living as a girl for around one year. Tessa and her older sister Zenia been conscripted as flowergirls at their cousin's wedding, and her mother had taken them into Chamberlain for the fitting. They'd gone to a bridal store called Something Blue, where the attendants had made an enormous fuss over her, utterly captivated by her long blond curls and huge cloud-blue eyes.

Being barely twelve (and looking about ten) they hadn't bothered taking her into the fitting room; opting simply to undress her in the showroom right down to her underthings. She'd been too surprised to even protest her disrobing; within seconds, she had climbed out of her jeans and t-shirt and was being led by the hand to the middle of the floor with her white cotton underpants on full display.

Tessa had been completely embarrassed: they were treating her like a little girl; standing her on a leather-bound footstool in her bare panties while they took her measurements. She was in high school now, almost a teenager; she didn't walk around in her undies like a six year old. Worse still, her sister wasn't made to bare her panties in public; Zenia got to have her fitting in private!

Strangely, she had experienced another feeling, hot and bright and skin-tight, a sense of pleasurable vulnerability she'd never known before. It was an emotion for which she had no word, something trembling and deep, poised halfway between bliss and ecstasy. She'd felt utterly and incomparably beautiful, like the princess in the fairy tale.

The same feelings of exaltation and arousal coursed through Tessa's thighs and belly while she waited patiently for the filming to begin. She was having difficulty keeping still; she had no idea where to put her hands. Hiding her cleavage left her panties exposed; so much of her body was on exhibition.

She'd been standing on the set for nearly twenty minutes while the director held a confab with the assistant and the FM; her embarrassment and sense of dishabille increasing to an intolerable degree. She would have given virtually anything for a brief robe to cover her modesty, but her pleasure at being forced to wait in her bras and panties was undeniable. Her breasts were straining at their tight satin restraints, throbbing gently at their pert pinkish tips. She looked over to the director's committee. The creativity conference seemed to be going on forever! How long were they going to make her stand here like this, the only girl in the studio stripped to her knickers? It was so unfair!! Did they actually think she had nothing better to do than show off her underwear to a hundred perfect strangers? Tessa thought about the script (such as it was), trying to distract herself from her semi-nudity. She'd seen the storyboard that morning, so she had a good idea what she was expected to do.

Her first scene is an extreme close-up of her face as she opens the bathroom door, her platinum blond hair moist and gleaming. Grinning a naughty little-girl smile, she looks both ways to make sure no one is watching, then scampers along the passage way, tossing aside her towel to reveal her brassier and briefs. The camera then follows her on a hundred yard flash through the household. Darting into the living room where one of her roomies is ironing a blouse, she pauses to glance at herself in the mirror over the mantle-piece, before flitting out to the central hallway waving to her friend as she goes. Glancing at Tessa's panty-clad figure, the girl laughs and shakes her head.

Heading for the staircase, Tessa passes another one of her flatmates, this one holding an animated discussion on her cell phone, who gives her a friendly slap on the tushie as she rushes up the stairs, damp hair flying. Still grinning wide – but eager to hide her undies from public scrutiny – she turns right at the top, dashing through her door with a silvery laugh.

Her second scene, which appears later in the commercial, takes place in her bedroom. Dancing before her full-length mirror – brush in one hand, blow drier in the other – she allows the camera a generous view of her nubile young body: her lean, slender legs and shapely round bottom; her curvaceous hips; tiny, waspish waist and perfectly sculpted breasts.

Tessa imagined it would be the best scene of the commercial: a pretty teenaged girl bouncing around in a tight satin bra and pink, gossomer panties, her hair flailing around her broadly smiling face. The sequence ends with Tessa colouring her lips cadmium red with a stick of Carmine Nights, winking cheekily at the camera: I knew you were there all along!!

"Tessa?"

It was Lois, the director's assistant. Evidently, the creativity conference was finally over.

"Are you OK? You're looking a little flushed."

"Just a touch of backstage nerves," Tessa smiled, "this is my first time before a TV camera."

Lois patted her hand sympathetically.

"You'll be fine. Come on, the shoot's underway, and you're up first."

Butterflies began dancing in Tessa's tummy as she felt herself led by the hand across the set in her lingerie. Her cheeks flared like a pair of valentine roses, and her heart slammed into overdrive. The time had come: the lights overhead flooded the set with brilliance, cameras were trained and focused.

It's happening, Tessa thought breathlessly.