I feel like the spy who saved the world. The monumental improbability of the scheme that I pulled off this week will never be recognised except by the two people closest to me in the venture, and in many ways neither of them knows the entire story. To be sure, it is not as though I have gone completely unrewarded; indeed as I write I can feel a tingle of excitement spreading through my loins at the memory of what I did ... and what was done to me.

The first piece in the jigsaw fell into place on Tuesday evening. I was lying in the Sick Bay recovery cot with Mr Gallows – the Headmaster of our privileged Sydney boarding school – quietly basking in the afterglow of sex. We have been meeting after lights-out in Sick Bay a couple of times a week for about a month – we simply could not find another appropriate location for a schoolgirl and a headmaster to make love.

I was wearing last year's way-too-small and no-longer-appropriate-for-public-exhibition school dress, now a traditional lovemaking prop that enhances sex play for us both. Properly donned – if there can be such a thing with this dress – it is several sizes too small to comfortably contain my swelling 8C breasts and the hem line covers my panties by a scant few inches – if I'm wearing panties, that is – which tradition also dictates that I must not. On this occasion I was indeed sans panties yet again, with the dress – improperly donned, some might say - unbuttoned to my midriff and the hemline hiked up to my 20" waist.

That's not to suggest I was indecent, though. I was still wearing a red lace bra that was almost covering my nipples (a state of affairs that I blame squarely on Mr Gallows' insistent tongue) and my hairless pussy was modestly covered by his right hand. He was lost in his own thoughts playing a favourite game, where he probes at my entrance and tries to withdraw before I can trap his finger in my labia by flexing my powerful pelvic floor muscles. I play along, but his fascination is so focussed I'm beginning to wonder if he realises that I am watching him and I decide whether he wins or loses. Men!

Our lovemaking that night had been beautiful and slow. Every time he enters me is like the first, the thickness and contours of his 9" cock slowly filling and parting the tight confines of my vagina. He relishes the slowness too as the constricting grip and heat of my love canal holds him perpetually on the edge of orgasm.

Looking down at him I felt a pang of regret and wanting; once again only the first two thirds of his now flaccid member were coated with my juices. At 4'11" and three quarters, my petite size makes it impossible – well, virtually impossible – for me to accommodate his entire manhood. Reading my recollections of our first encounter (which I do a lot) I wonder if I will ever feel all of him inside me again. Here's what I wrote:

"The release triggered a second orgasm. Screaming again with the unbearable pleasure I hooked my heels behind his buttocks and pulled in with all my strength, forcing his manhood deeper inside to fill the space created by his explosive stream. With the exquisite pain of his pulsing knob driving up into me, a third crescendo rocked my body, this time my own gushing ejaculation mixing with his and washed over his balls, now pressed achingly against my incandescent labia."

Wow! Heady stuff, Belinda! I'm tingling again with the memory. Our sex is different now, sweet and sensual rather than animal and uncontrolled. Not that I'm complaining; that climax was not without a cost: I couldn't walk the following day and I begged off school complaining of stomach cramps (I didn't think 'bruised vagina' would work as well). At lunchtime – after seeing the absentee list – Mr Gallows sent me a sealed note hand-written on his office stationary:

"To whom it may concern, Belinda is unable to attend class because of the cataclysmic fucking I administered to her in my office. Sincerely, John Gallows, Headmaster."

I laughed so hard it hurt, but pretty much everything hurt that day. I still have it locked away in the secret drawer of my keepsake box.

Selfishly, I desperately want to feel him balls-deep inside me again, but I want it for him just as much. He never loses control with me; never drives deeper than the seven inches he knows I can handle. I so wish he could just abandon control as I had and pound his full length into me, not just once but again and again until he came deep inside me.

Thinking of others before myself (well, maybe thinking of myself a bit too) ... maybe I'm growing up?

The next night, the second jigsaw piece – seemingly unconnected to the first – fell into place and my plan was born.

The senior girls' dorm is only very lightly supervised and – if I'm honest – we exploit their trust a little. Once dinner is eaten and homework is done we have the evening to ourselves because the staff are all busy mothering the junior girls.

Mr Gallows would have a fit if he ever found out what we get up to – at the very least he would demand videos. We spend half of our time talking about boys (most of us have never actually slept with a boy) and the other half exploring our sexuality with the collection of vibrators and dildos bequeathed to the dorm by senior girls over the years.

On Wednesday we played Reverse Tug of War. I sat it out and watched frustratedly hoping for Stalactites. Reverse Tug of War is played between two girls using my favourite dildo Silver – a double-ended 18" rubber shaft. An elastic band is tied around the middle and – well, you get it – first to the middle wins. Fully stretched, my pussy is only 7 inches deep so the best I can ever hope for is a draw.

Sometimes I challenge my best friend, Trish. She's six feet tall, athletic, small breasts, long auburn hair and pale Gaelic skin. She's one of the few girls who can reliably take a full half of Silver without pain. I can't beat her, but I enjoy getting her about 8 inches deep then gripping Silver with my secret muscles and fucking him back and forth inside her before I let her win. It makes for a good show and gives the new girls the courage to give it a try.

That night's game will go down in dorm history; stories will still be told about it when my grand-daughter enrols in the school. Trish challenged my new room-mate, Rupali. Rupali is 6'1" tall and built like an underwear model: long, shapely legs, slim hips, a very narrow waist and full breasts that defy gravity. She has coffee-and-cream skin and gorgeous cascades of long black hair, cut into bangs at the front to frame her high cheekbones.

New to the school this year, she joined Trish on the Girls 1st netball team playing Goal Shooter (Trish plays Goal Keeper so they are at opposite ends of the court and have little interaction – until now). I went along to the game on Monday night to support Trish, but couldn't take my eyes off Rupali. And I wasn't the only one; a group of boys had learned of her selection and filled the front row of the bleachers in the gym. The netball uniform is an old-fashioned, box-pleat skirt in the school colours over a high-cut, sleeveless, black lycra leotard. Since netball skirts are so short and players do a lot of jumping and pivoting, the girls choose to add a modest pair of black lycra athletic shorts. The black ones aren't sold in the uniform shop and – this being her first game – Rupali didn't have any so she played in just the leotard and skirt.

The boys were spread right out along the front row as the game started – presumably to get the best angle on the girls' legs – cheering and yelling and completely oblivious to the rules. A few minutes in, a long, fast pass from our Centre came flying into the goal circle; Rupali leaped straight up at full-stretch to take the ball, her pleated skirt ballooning out to display her long, bare thighs all the way up to the hip and the narrow strip of lycra stretched tightly across the mound of her pudenda. I shocked myself by gasping a little even though I see her in her underwear every morning.

The front row fell into a shocked silence and then – as Rupali made the goal – there was a frantic jostling for position as all of the boys at the defensive end raced for the spare seats in the second and third rows in attack. I went down at half-time to tell her the fan-club was in her honour; she was flattered but not embarrassed and I was surprised to see a lot more twirling and jumping from her in the second half. Mynx!

If those boys could see her now - red satin nightie, panties off, lubricating herself and her end of Silver – they would have a coronary. Despite our auto-erotic games in the dorm, I have always thought of myself as very much heterosexual, so I was surprised and a little shocked at the warm tingle of excitement I felt watching the girls getting into position. They sat on the floor facing each other, long, shapely legs scissored together, each with one head of the 18" Silver nestled in their vagina. I caught myself studying Rupali more closely than I should have been and felt a flush of shame mixed with excitement. Her pubic hair was trimmed short and shaved into the shape of a small apostrophe above her sex. Her outer labia were completely shaved and now spread wide around Silver's girth, showing pink glimpses of her inner womanhood at the edges.

I dropped a hair ribbon between them to commence the match and both girls greedily gobbled four to five inches in a single thrust. Oh my Lord! It takes me minutes to work that much cock into my tiny pussy and these two Amazon goddesses managed it in a couple of seconds. There was a respectful gasp from the 10 girls assembled to watch and more than a little sympathetic clenching of thighs – myself included.

The easy bit over, Trish leaned back expertly, relaxing her muscles, straightening her hips and keeping her clitoris away from contact with Silver. This earned her another inch or two and Rupali – seeing the sense in the strategy – copied. Both girls had about six inches – enough to fill me up completely – and were working against the friction, lifting and rolling their hips; stretching their vaginas and trying to upset the other girl's angle of entry. Their breathing started coming in panting gasps as each girl's gyrations caused Silver to dance and buck deep inside the other. Before long both were glowing with perspiration.

The audience watched on, completely rapt now and I noticed several hands disappearing up nighties as the tension mounted. Both girls made it to 8 inches and were obviously full. With Silver now pressing against the backs of their vaginas, legs locked tightly together and engorged lips separated by less than two scant inches of rubber shaft; they were forced to move as one, lifting and thrusting in unison. With one last desperate push, they lunged towards each other and in an instant their labia met, hiding the centre marker from view so that nobody could tell the winner.

Incredibly, neither of them stopped and 10 pairs of eyes stared jealously as these two tall, beautiful girls – heads back, eyes shut and gorgeous long hair spilling around their shoulders - moaned and vocalised their pleasure as they ground together at their centres; lips meeting, pressing and spreading like a passionate kiss.

Rupali grasped at Trish's hips for better purchase, they bucked and ground as a single being, moans building to screams with impending mutual climax. They came together, backs arched and crying out in ecstasy, writhing and trying to move against each other but unable to because of the shaft that joined them. I heard several gasps as some other girls climaxed under their own touch and looked down, no longer surprised to see my own panties soaking wet. I surreptitiously reached down to rub and squeeze my clitoris in a fruitless effort to relieve the heat and longing there.

Their single sexual body became two again. Rupali unlocked her long brown legs from Trish's midriff and slid backwards, disgorging the seemingly endless length of Silver, her inner folds clinging to the shaft as she withdrew, grudgingly relinquishing their hold as each of the 9 inches slid between her thighs. A look passed between them; not embarrassment, but an understanding that neither had intended this to happen yet neither felt any regret.

The silence in the room was palpable. To break the tension, I suggested "Rematch?" in a voice that sounded far steadier than I felt. There was laughter all round and several girls – those who had not yet come, I noticed - crept quietly off to their own bedrooms to minister to their own needs. I tidied the cushions and made myself useful washing Silver while Rupali pulled on her panties and straightened her nightie, then we switched the lights out walked together in the dark to our shared bedroom.

Later, lying in bed I heard her sobbing softly across the room. I listened for a while, not knowing what to do or say.

"It doesn't mean anything you know," I said. "Coming, I mean. It doesn't make you a lesbian or anything. I've come plenty of times playing games with the toys."

"It's not that," she whispered in hitching sobs. "I like boys and girls, I've known that for a long time." The tickle of excitement in my stomach was starting to feel decidedly familiar now. She continued: "But that was the first time I have ever come."

I wasn't sure what to say to that – I thought it would be good news, not bad. I knew she had slept with a boyfriend at her previous school. I was surprised she had never climaxed. "What about your boyfriend?" I asked. "Didn't he ... you know ... look after you?"

"He tried," she explained. "But he was only 7 inches and I never felt... , " she searched for the right word, " ... full ... like with Silver." And then with a voice hitching with tears, "I thought I would never have an orgasm, and now I finally have one and it's with a girl. What if I never come with a man?"

Sweet baby Jesus! Talk about first-world problems! I dreamed about issues like a 7 inch cock and coming with a 9" shaft deep inside me.

"Wow" I said, surprised. "Didn't Silver hurt? At the end?"

"Not at all. There was some stretching, but it was beautiful, touching me in a way that a man never will."

Never say never, sweetie, I thought to myself. From personal experience you just never know when you'll be kneeling splay-legged before a man with his hand up your school dress stroking you to orgasm while he's inviting you back for a night of cataclysmic fucking on his 9" cock. Just saying, you know.

I fell silent in my own thoughts for a while and then, changing subject: "Rupali, you're Indian right?"

"My parents are," she said. "I'm Australian, I guess."

"Aren't you supposed to be a virgin?" I asked candidly. "You know, for your wedding night?"

Her musical laughter lifted me up and made me smile in the dark. "No," she said. "My parents have embraced the Australian way." And then with some sadness in her voice "I will choose my own husband, I suppose."

"Isn't that a good thing?" I asked, wondering why anyone would like their partner chosen for them.

"Maybe," she explained. "But there's something indescribably sexy about the idea of going to bed with a man you have never met." She paused, wondering how much to share. Then, with some excitement: "Don't you fantasise about a stranger? You've never seen his face, never felt his touch, and then his cock – one that you've never seen or felt, so you can't know how big it is – slides inside you, but slowly! You don't know anything about it – he's behind you, so you can't see – and every inch that goes in might be the last, but maybe it's not, maybe he fills you up and there's still more."

Wow! My nipples went hard. But I said, "That doesn't sound like an arranged wedding to me. At the very least you'd see your husband at the wedding."

"True, but it doesn't hurt to fantasise," she sighed.

We were quiet again for a while. I heard her breathing deepen as she neared sleep.

"Rupali?"

"What?" she replied sleepily.

"What if I could make it happen? You know, what you were talking about before."

"Belinda," she said in a dreamy voice, "you make that happen and I will stick my tongue so far up your tiny, tight snatch you'll come out my ears." Then she fell asleep.

Oh. My. God.

It would be a long time before I got to sleep that night.

And so a plan was born.

On Friday, the last and most delicate piece of my master plan slotted into place. I met Mr Gallows in Sick Bay as usual. We kissed and petted for a while and then – when my tiny school dress was in a suitable state of disarray – we moved to the examination bench for lovemaking.

I stood on the wooden step that patients use to climb onto the bench; bent over with one knee hooked up onto its flat surface. With my dress pulled up around my waist, I arched my back to present my shaved, gaping pussy to Mr Gallows' standing behind me. He reached one hand under my dress to stroke my breasts while the other guided the tip of his cock to my entrance. I waited until he was at his most vulnerable (though I concede that the opposite may have appeared more true); he pushed the first few inches into me and was waiting for spasms in my vagina to abate as I adjusted to his size – then I struck.

"Sir?" We still addressed each other formally; for one it reduced the likelihood of an embarrassing public scene and for two ... well ... we both found it kind of sexy.

"Is this important? I'm kind of busy." His pleased tone made a lie of the words. He has come prematurely on a couple of occasions and is most at risk upon entry – when I'm at my tightest. Conversation helps him regain control, so it was a welcome diversion. I once offered to masturbate beforehand so that my pussy would be ready for him – he forbade it. Hey, he's the boss.

"Do you have any fantasies?" I asked baldly.

"Yes. I want to ram this thing so far into you that you speak with an accent," he joked. But was it joking?

I joined in, laughing "My Mum speaks with an accent" (she's French). "You didn't have anything to do with that, right?"

"I wish," he said under his breath.

"What!" I laughed in surprise.

"Belinda, this might be hard to hear, but your Mum is smoking hot."

Sigh. I already knew that.

Back on topic, though: "Seriously, that's your fantasy? To go balls-deep in me?" I asked.

"No, hey, don't get me wrong, I don't want to hurt you," he backpedalled. "Or any woman for that matter – I've never been able to do it before. It doesn't stop me wondering what it would be like though – to not have to worry about it."

Confirmed: excellent. Now, close the loop, Belinda.

Our conversation had done its job and he was slowly working his long cock deeper into my pussy. I was impatient for the moment when he would reach my innermost point and start pumping me harder.

"I was reading this book – Ingenious Pain by Andrew Miller... ," I began.

"I've read that," he interrupted. "Great book. Great insights on what makes up our soul. It's not on the scholastic list, though."

I pressed on: "There's this scene where a woman is skating on a frozen pond. Suddenly she's ravished from behind by a mysterious stranger, but she doesn't mind, in fact she wants it to happen. He just lifts her skirts and starts fucking. Then he disappears unseen. The fact that it could have been anyone is part of the appeal to her."

He started laughing, his cock pulling deliciously against me with the effort. "Is that really your fantasy, Belinda? What you've just described is the fantasy of every boy in the world old enough to masturbate to internet porn. I wish I found you 20 years ago."

"No, it's not my fantasy. I was just curious; it seemed a bit ... scary. What about older guys, why don't they get off on that?"

"Oh, we do," he said. "We just recognise the paradox."

"What do you mean?"

"Well, it's impossible, right. If she doesn't want it, it's rape, and that's not sexy. So you would have to know she wants it, and then it couldn't be a surprise. Paradox!"

Stretched and lubricated now, he started stroking into me with an increasing rhythm – just the first 6 inches – while massaging my breasts and pinching my nipples. I stopped talking and just enjoyed the ride – that wonderful feeling of friction and fullness. He came before me but – at usual – the extra pressure created by his cum spurting deep inside me triggered my own imminent climax.

As we lay together afterwards I asked "What if there was no paradox? Couldn't someone in the middle set it up without either person's knowledge?"

"Now THAT, Belinda," his hand under my dress, stroking me back to readiness, "THAT is the ultimate fantasy. Sign me up when you work out the kinks."

That's a promise, I thought.

With all the pieces now in place, it was just down to execution. If this went right, I could fulfil the sexual fantasies of two people in a single stroke. Maybe three, I wasn't sure yet. But if it went wrong, I could ruin lives. The stakes were high, but the risks were low; I was confident of my players in this production, they just needed to play their part. (Spoiler: they did).

Saturday night was the night. It was usually pretty quiet on Saturday; all of the day-boarders go home for the weekend and only the full-semester girls remain. Legendary things don't usually happen on Saturday because it's no fun without everyone to share the experience.

After dinner, I was in my room listening to music – I don't know where Rupali was – probably at the gym. I sent a text to Trish (she was probably just down the hall, but mobile phones are a curse of our generation, right?)

"Playing 'What's up Doc'. My place 11:30pm. Bring your roomie. Rupali's in."

Then one to Rupali:

"New game. Our room 11:30pm. Trish is in."

And another to Mr Gallows:

"Fantasy night. Teachers' lounge 11:45pm. Wait for me. Wear a hoodie."

And I waited. That was the hard part.

Rupali came in at 8:30pm wearing just a crop top and bike shorts. The tight lycra clung to every curve and she was glowing with perspiration. Been for a run, obviously. "Hey babe," she greeted me. She was still catching her breath as she sat on the floor stretching down. Long, beautiful, legs spread wide and flat on the floor she reached for one foot, her full breasts parting against one knee and hair spilling over the top of her head, hiding her face. I stared openly, not tingling any more, just wanting.

"What's the game?" she asked, not looking up.

"Huh?" she startled me out of my study of her gorgeous body.

"Your text. What's the game?"

"Oh. 'What's up Doc'. We haven't played since last year, but you're not the only newbie, Trish is bringing Mandy." I explained the rules: 'What's Up Doc' is a guessing game. One girl picks an item from the dorm and slides it into the pussies of the other girls – who are blindfolded of course – until one guesses right or all pass. The girl who guesses correctly gets to go next. It works best with small groups – it's faster moving and easier to keep a lid on the peeking.

"Sounds fun. Trish is coming?" Seems like she was hoping for a repeat of Thursday night. I was hoping for something better.

"Yep; and Mandy. Just the four of us. We'll play in here."

"Cool." She was in. She stripped off her crop top and shorts ready for the shower. I was trying to play it cool but I couldn't help watching. Her large brown nipples were fully erect from her exertions and she rubbed them with her fingertips to get them to sit down again. I imagined putting one in my mouth when her long eyelashes flicked in my direction. I was sprung.

She was standing naked in front of me – watching me watching her – but I couldn't look away. With a swish of long black hair she pivoted on one foot and turned away. Facing the door now – very slowly and keeping her legs straight – she reached down to the floor to pick up her sweaty clothes, holding the pose for a few wonderful seconds. I let my gaze run all the way up those long, long, legs; lingering at the top to study her shaved brown pussy lips bracketed between perfect buttocks and thighs.

"Jump shot!" she sang, suddenly leaping up, full breasts bouncing, and tossed her clothes towards the hamper. She looked at me, winked, then grabbed her robe from the door and left. You know, I was beginning to think that show was for me.

When she returned 10 minutes later, we both pretended nothing had happened and went through our bedtime routine, waiting for the dorm to quieten down. We lay in bed gossiping and giggling quietly in the dark when we heard a quiet tap on the door. It was 11:30. Deep breath, Belinda; here goes.

I slipped out of bed and let Mandy and Trish in before turning on the light, both girls were wearing short satin nighties (de rigueur for 'Whats Up Doc') and great big smiles. Mandy is about 5'6," skinny, small breasts and bony hips. She's cute in a geek-chic kind of way: a slight overbite, black framed glasses, white teeth and clear skin.

As I tossed some pillows on the floor, Rupali swung her legs out of bed – three pairs of eyes watched every movement as she folded them gracefully beneath her bottom, sat down, and smoothed her maroon nightie (what little there was of it) over the tops of her thighs.

Trish flashed me a conspiratory glance and suggested Mandy go first since she has not played before. This was also true for Rupali, but she didn't say anything. I knew what Trish was doing, so I agreed.

"OK," I instructed Mandy. "Go out and grab something from the dorm and bring it back; we'll be blindfolded. Only rule is it has to fit in our pussies. Remember, I'm small and I haven't had a turn yet, so keep it sensible."

Mandy slipped out silently with a big goofy grin on her face and Rupali handed silk scarves to me and Trish. She kept a giraffe-print one for herself that I hadn't seen before; it should have looked kitsch but instead it contrasted exotically with her glossy black hair and coffee-and-cream skin. We slipped off our panties and waited for Mandy to return.

There was a quiet knock at the door and Trish grinned at me again as we lifted our blindfolds and raised our bottoms in the air, ready to play. We heard Mandy sneak in behind us. "Ready?" she asked.

"Banana!" Trish and I sung in unison.

"You bitches, you peeked," Mandy sounded betrayed.

"No, we didn't," Trish laughed. We all pulled down our blindfolds and sat up. "New girls always pick a banana; it's like a tradition."

Rupali got the joke and started laughing too. Mandy looked at us again, realised she had been had, and joined in.

"Me next," said Trish, slipping out the door.

I handed a spare scarf to Mandy. She stepped out of her panties and we all turned around: head down and bottom up, ready for Trish. She returned quickly – that meant she had been planning ahead. Bad news.

"Ready B'lin?" It seemed I was to be her target for this prank.

"Sure, you only live once."

I heard a squirting sound from the bottle of lube. "If that thing's thicker than a banana," I threatened, "I'm coming back in here with a leg from the coffee table." Nervous giggles all round.

"Don't get your twat in a tangle," she admonished, then "Here it comes!"

Holy crap! It felt like I was being doggy-fucked by Frosty the Snowman; it was freezing. My tiny pussy clenched in shock. "Loosen up, Blinny," Trish said, "or I'll have to leave it in there all night."

The initial shock had worn off and I realised it really wasn't as cold as I initially thought. Whatever it was had come from the fridge, not the freezer. Blood was flowing back into my veins now, so I relaxed and set to work trying to guess what was in my snatch. I only had an inch or so, so I asked: "A little more, please." Trish slipped another inch inside me. The fresh coldness contrasted with the now warmer part and gave me a pleasant shiver. I thought it felt bumpy. "Twist it please."

"My pleasure," said Trish. "Hang on, no, it's yours you horny slut." More giggles. She twisted the shaft inside me. Definitely bumps, round profile and cold.

"Gherkin," I guessed.

"Loser!" she trilled merrily, whipping it out of my hole. "Next."

I left my blindfold on as Trish moved behind Rupali. I could hear her breathing beside me, maybe a little nervous. Blind, I groped about for her hand, found it and gave it a squeeze, which she returned. Still holding her hand, I shuffled a bit closer and we settled our interlocked elbows back on the floor. Our heads nearly touching, the scent of her shampoo filled my nostrils, coconutty and tropical, making me dizzy.

Her hand jerked in mine. "Oh!," she uttered in surprise, then "Mmmm" as it turned to pleasure. Sounds like Trish had started.

"More please," she said in a husky whisper, right next to my ear. At that moment, totally unbidden, an image so complete and so perfect in detail popped into my head ... it was almost real. I was in this same position, crouched over on knees and elbows with my bottom in the air and holding Rupali's hand, but in my image she was beneath me instead of beside me. Her slim arms were raised behind her head, long black hair fanned out beneath them. Our bodies touching, breasts pressed together, her legs locked around my waist. We weren't eye-to-eye, but cheek-to-cheek, her lips close to my ear as in reality. I rearranged my pillow long-ways so that I was straddling it, pressing it into my stomach, my breasts and my pussy, thus completing the illusion.