"Friends! We weren't friends! I was deeply in love with you."

Last week Mary-Anne Price took lunch with a girl from her boarding school she had not seen for decades. It was no ordinary lunch

It used to be a well recognised phenomenon in girls' boarding schools. At mine, it was known as "having a pash" on someone. Others schools called it a "crush" or a "squeeze". From the age of 13 until I was 17, when she left, I "had a pash" on Sylvia. I loved her more single-mindedly than I have loved almost anyone else in the 40 years since. There have been one or two obsessional passions for men that equalled - not exceeded - my passion for her, though never another that was entirely platonic, utterly faithful, endured for four years and was conducted throughout in total secrecy.

I seldom looked directly at her in case I gave myself away, but she could hardly have failed to notice the number of times I stood "accidentally" near (never next to) her in the lunch queue, or how often I just "happened" to sit at the table she headed. We rarely spoke. I did not send her presents or notes, and we did not touch until the day she left.

Sylvia dominated my adolescent years. During the term I knew exactly what she was doing and where she could be found at any moment of the day. During the holidays I thought about her for hours and composed cool, sophisticated letters inviting her to stay. "You'll be bored to tears I'm afraid, especially by my wretched little sister, but we might find something amusing to do ..." These letters were not sent. I never saw her in the holidays. Time dragged through dry and dusty weeks.

Some girls exchanged notes with their pashes, and kittenish, clingy little kisses at bedtime. Some seniors came into the dormitory after lights out to give their adoring junior a good-night hug. This had nothing to do with lesbianism, of which we were entirely innocent. Most of us were like playful young animals in the spring, heaving and butting, practising our emotions for the time when we would meet boys. There was an advertising slogan at the time: "preparing to be a beautiful lady". We were preparing to be devoted wives, getting ready to fall in love, an event that would be followed by a chaste engagement, the prelude to a thoroughly suitable marriage.

My love for Sylvia went beyond emotional rehearsals. I watched her, thought about her, drew endless calligraphic doodles entwining her initials with my own, copied her handwriting until I could forge it to perfection (because writing like her made me feel as if I had become her). I knew what book she was reading, what pop song she was humming (probably something from Oklahoma! or Seven Brides for Seven Brothers), what school meals she liked best, her place on the deportment board (low; Sylvia slouched, probably on account of her height). I even knew the dates of her period.

Whereas most girls whispered and giggled about their pashes and changed them every term or so, my passion for Sylvia never wavered.

She left at the time I moved into the Lower Sixth to start my A-levels. She turned up at school once or twice, waving from the front seat of open- topped sports cars driven by glamorous boyfriends. They would be granted permission to take me out to tea, since my parents lived abroad and I hardly ever had visitors at parents' weekends.

Sylvia would say kindly that she liked my hair done in the new way or that my powder (Cussons' Jasmine, puffed lavishly under the armpits after my morning bath) suited me. Gauche and hideous in NHS spectacles and pudding- basin haircut, I would blush and be too shy to compliment her in return. She must have known she looked wonderful. The taciturn, lantern-jawed boyfriend must have told her so all the time.

A couple of years later, I too left school. But although we met once or twice - for lunch in Dickins & Jones or tea at the Lyons' Corner House beside Charing Cross station - we were ill at ease. We were supposed to be equals now, both of us young women out in the world - yet how could I ever be her equal, dwarfed at the foot of her pedestal, gazing upwards?

Last week I saw her again for the first time in 35 years. I was dimly aware what had happened to her ... an early marriage followed by a quick divorce and some wild years, culminating eventually in a stable and apparently happy marriage to an Australian. I heard that she had two children. She came to England occasionally, and on one of these visits somebody gave her my telephone number. She rang and left a message. Luckily I was away, and by the time I was home again she had left London.

Next time she wrote a postcard, letting me know in advance when she would be "in Town". I ignored the postcard. I didn't want to see her. I didn't want to know if I still loved her. I am a grown-up woman now; middle-aged, a grandmother. How old must that make her?

Finally, she took me by surprise. The phone rang beside my desk one morning. I picked it up - crisp, formal, preoccupied: "Hello sweedie," she said; "It's Sylvia." Sweedie! The sound of that word poured back after 40 years like water rippling down a sluice. The bantering way in which she always said, not sweetie but sweedie. "I'm in London with my husband. Be lovely to meet."

I arrived late at the restaurant. She was already at the table. As I threaded through the lunchtime crowd I spotted her, an old lady with deep, dark bags under her eyes and a pattern of diamond-shaped wrinkles crisscrossing her face. She wore no make-up. Her skin was dry. Her hair was grey. She smiled brilliantly. "Mary-Anne! How lovely to see you!" We did the double social kiss. She smelled powdery.

Quickly, quickly I ordered a glass of white wine. She changed her mind and joined me, clinking her glass against mine. Why late. (Excuses.) Number and sexes of children. Pull out photographs from handbag. Look: this is my partner - pity he couldn't join us. Mine flew home yesterday, she said.

For five minutes I didn't draw breath. Who you still in touch with from school? Remember Gillian? Felicity? Valerie? Jennifer? (Fifties names.) What you going to eat? Everything's good here. Wine - let's have a whole bottle. Celebrate. You've aged well. "Have I?" she said. "I'm going to be 60 this year. Hard to believe." Her mannerisms were the same, and the colour of her eyes and the shape of her nose. Her voice had not changed, not even after 25 years in Australia.

What was different was our memories of those distant schooldays. She remembered us as friends. "Friends!" I expostulated. "We weren't friends! I was desperately in love with you!" She looked aghast. "I had no idea!" It is impossible that she did not know. "Sylvia, are you pulling my leg?" "No," she replied - "are you?"

I ached for the sadness of her life. Her mother had called her "fishface" and as a result she always thought herself ugly. Too late now to tell her that she had glowed and undulated like Milton's Sabrina fair. Too late to try and tell her what she had meant to me.

My guts writhed when she described her years of poverty, her hard, narrow life in an Australian outback town - my Sylvia, who could have conquered the world with her beauty and spirit, her flirtatious intelligence. At least her destiny had not been banal.

Her face became young under my gaze, her eyes grew large and round, she tossed her head and teased a tendril of hair through her fingers. I learnt the names of her children and was shown their photographs: healthy, uncomplicated young Australians with no trace of the bewitching naiad their mother once was.

We parted after two, both a little drunk. I paid the bill, though politely, generously, she offered to split it. We said we'd meet again next time she came to London. I would prefer her not to ring, but if she does, I could not resist.

At home that night I found myself reckless, wanton, desperate to make loven