They could hardly have been more different physically, these two girls sitting opposite me at Gate 10 at Luton airport, waiting for the fight to Edinburgh. Sophie was tall and slim, her immensely long legs shown off in no uncertain terms by the fact she was wearing loose sports shorts of the kind that might have been used by female hockey teams, if they don't still wear miniskirts in these joyless, wary days. She had long blonde hair and a ready laugh in which she threw back her head.

Tara, on the other hand, was a little shorter, less lithe, and less confident in her body. She had small breasts and was fuller in the beam around her hips and legs, which were shrouded in a sensible brown skirt. She did, though, have beautiful shoulders and arms finished with pale, creamy, smooth skin. Her face was that of a bookworm, a studious type, with a little button nose and rosy cheeks. Her mousy hair was pulled back with a scrunchy. She looked as if someone was keeping an eye on her development and making sure her arrival at womanhood was not accompanied by any suggestion of sexual interest.

Tara had avoided my gaze at first, and I had reined it in accordingly, but my eyes were constantly drawn back to her face, her creamy arms and shoulders, her flat chest, and that discreet brown skirt and all it contained. Gradually, she gained confidence and her eyes flicked across mine, meeting with a tiny flash that brought a suggestion of acknowledgement to her face. She didn't know how to handle this, being given "that look" by a man who was older than her and disturbed by the boys who came skittering into her orbit ever few minutes, mainly to flirt with awkward grins at Sophie.

I couldn't work out what kind of group they were. They were a little too old for school but too immature for university students on a field trip. Immature, that is, all except Tara, who was an old soul in a young body. I could see her getting railroaded into a relationship with some young fogey and ending up as frustrated at thirty as a middle aged woman, working as a teacher and being dowdy, pleasant Mrs Respectable, with 2.4 children and 0.75 of a husband, the missing 25% being the part that could stir her blood.

I wanted to save her from that fate, not by marrying her myself but by giving her some naughtiness to look back on and maybe to replicate from time to time. I wanted to show her how to give in to her desires and how to impose them on men.

I was wondering how to literally cross the divide so I could sit next to them when one of the Sophie fans hurtled in and plonked himself down on the other end of the bench of four seats I was on, jerking it up like a seesaw because the legs weren't equal or the floor wasn't level.

"Oh, Justin!" Tara exclaimed. "You've spilt the man's coffee." Justin muttered apologies and dashed off again.

Sophie dragged her giraffe legs up and straightened her back.

"You'd better come and sit over here," she said, "or you're going to get that all day." As if to demonstrate the point, an elderly man shuffled into the picture and sat down where Justin had been, causing the same kind of jolt. There was something sexy about being jerked upwards in front of these girls and we all laughed nervously. Tara stood up and moved to the next seat so i could sit between them.

So there I was, happily placed between Miss Sexy and Miss Fascinating. Without intending to, I slapped a hand down briefly on Tara's left knee and Sophie's right.

"That's much better, I said. "Thank you, ladies." Neither of them had flinched at my hands, although I fancied I felt Tara tense a little. We fell into conversation. They were a youth orchestra on an exchange trip, their last concert before most of them went off to uni. Sophie was a cellist and I could well imagine her with those wonderful lower limbs cradling her instrument, just as she was destined to cradle a succession of men as their eager penises sought out her long, mysterious tunnel. She reminded me of Tilda Swinton's character in the film with Ewan McGregor where she plays the lusty, frustrated wife of a bargeman who gives the younger McGregor character a lift and when inevitably she and he fuck, outside on the canal bank in broad daylight, her left leg reaches for the sky.

Sophie would have such encounters, I had no doubt. My lovely Tara, though, would never put herself in such a position, and I felt it was my duty as her official admirer to make sure she had some excitement too. I found myself talking to her rather than both of them, and Sophie eventually stood up and wandered off.

Tara was a pianist but was being groomed as a conductor. We both tittered uncomfortably at the word: grooming is one of those terms that have acquired a new and unwelcome meaning that makes it awkward to use in its original context.

"You're being groomed?" I mused. "In a good way."

"Yes," she said with a barely suppressed snigger, well aware of the fact that it could sound like an accusation to a man like me. "Nothing could be more respectable and innocent than being groomed to become the conductor of an orchestra."

"You look pretty respectable to me," I said.

"Not innocent?" she said, almost choking on her own flirtatiousness.

"One never knows," I replied. "Do I look innocent?"

"You look respectable too," she said. "That's a decent basis to start from."

And indeed, it was a good basis for Tara and me. In those few sentences, we had become conspirators, answering unspoken questions so that we had leapt ahead in the getting-to-know-you stakes. We were going to be lovers, I could feel it. And more importantly, so could she. Tara had dipped a toe in the water of a love affair and she liked it.

We talked about music and then somehow got on to tennis but kept away from man-woman matters. I was invited to their concert - at lunchtime in a park - and she accepted my offer of a meal afterwards. By the time Sophie came back with three cornettos, Tara and I were an undisclosed but undoubted item in our own minds. I even managed to shrug off the thought of getting my head up her skirt and ventured into the fantasy of a personal relationship. Of course I had beautiful thoughts about sucking the girl juice out of her, about thrusting my hips between her thighs and plunging my cock into her, but I also thought about talking by the river with her, hand in hand.

The concert was okay if you like that sort of thing - a bit like going to watch a school play which you would never consider unless there was someone you knew in it and it would make them feel good. I like a few classical pieces, but not many.

The musicians were dressed in casual clothes: a deliberate move to make them more relatable to the young people in the audience. Tara had explained this to me at the airport, how they were determined to dispel the myth that classical music was for posh people. Even she had made an effort. Rather than the dull brown skirt she had traveled in, Tara was wearing a short denim skirt, although below it, black tights and big, heavy-soled black boots seemed to have been chosen deliberately to bring down the sexual temperature.

She was very impressive with a baton in her hand and seemed to command the respect of the orchestra. Even Sophie kept her eye on the conductor while involuntarily (I think) reinventing the cello as a sex toy, her miles of beautiful female leg flexing and relaxing as the music demanded. She seemed to be wrapped in a tight PVC outfit, neckline plunging of course and the skirt slashed to the crotch. Every man in the audience - and many of the women too, -must have wanted to take her behind the bandstand and devour her before plonking her back on her chair so they and she could get on with the music. Maybe female cellists have always had this effect on people, I don't know. But as sexy as she was, I kept being drawn back to the less obvious charms of Tara and by the time it was over I was salivating at the thought of what was to come.

With no instrument to pack up and look after, Tara was ready quickly and 20 minutes after the end we were on the sun-kissed terrace of a restaurant as Scotland basked in some very atypical good weather.

In the bright sunshine, her hair was far from mousy. It was a dozen natural shades of gold, lustrous and blending together seamlessly, making her look more of a nature girl and less of a nerd - although there is something sexy about a female bookworm, a sort of pent-up sexuality being subdued by an overactive serious part of the brain.

Naked at the shoulders again, she was ensconced in a sheath that would once have been called a boob tube, and the lack of a bra was further evidence of the fact that she had no breasts to speak of. She did have nipples, though, and I could sense they made her uncomfortable when she knew they were standing to attention under my thinly-veiled gaze. I could also sense that Tara was making an effort to shrug off her self-consciousness and be a proud young woman rather than a nervous girl.

She had the intellect it pull it off and a broad range in interests, so she could follow me down conversational diversions and introduce some of her own. With Taylor Swift in the country on tour - that being the main reason for the lunchtime gig, because 90% of Edinburgh's teenage girls would be otherwise engaged in the evening - we discussed that aspect of popular culture, with me treading carefully in the minefield of the current way of thinking and what was and wasn't "cool". I got the feeling she was treating me as carefully aa I was treating her. We were giving each other leeway and accepting there was more than one way to see many things. I wanted her to fit somewhere in my catalogue of "good woman" profiles and she wanted to see me as a nice man.

It was working well as we walked to my flat in a pleasant haze of white wine and good food. She was going to run a professional eye over my music collection, amused as she was at the fact that I still used CDs.

Tara's solid, functional body had nowhere to hide in the two tubes of soft cotton and denim, but I managed to keep my hands off her until we were in my front room with the sun streaming in through the French windows. Then I stood close to her and she melted into my arms. I kissed her shoulders and ran my tongue down her milk-white left arm and into her elbow, where the soft, unvisited flesh smelled lightly perfumed and very feminine. I ventured up her side to her armpit and we both realised we should sit, so we landed heavily on the settee and she leaned back obligingly, submitting to what I could tell she thought was an unusual desire to lick her in that potentially unsavoury place. Once I had begun, though, she relaxed and started to enjoy the feeling of being consumed by this hungry man.

My hand crept instinctively under the cotton to her chest and I scooped up as much breast meat as I could find.

"Nothing to see here, I'm afraid," she said in a commendable attempt to defuse an embarrassing situation for her.

I sucked her nipples one by one and she quickly understood that having no flesh there didn't mean she had no nerves and no connection to her central sex unit. She writhed as my tongue and lips sent messages to her vagina.

"Stand up," I urged, and she did so. I pulled her tights down and she sat again to remove them completely. Her knickers remained in situ where we could treat them as another fun fence to jump in our sexual gymkhana. I slid my hand into them and was pleased to feel pubic hair. I knew she would not be shaven down there, and I wanted the full experience of my face in a young woman's crotch, hair and sweat and all.

But first, I fingered her. I presumed she had been felt up before, if nothing else, but as my marauding finger entered her hole, I found myself trying to tell if there was still a hymen-tight entrance there or not.

I probed deep into her and she kissed strongly as she abandoned herself to her fate. I pushed her flat on her back and removed the knickers, then gave her an eager and comprehensive licking. She was rich and luscious down there and even spread herself a little more as she gained confidence.

"Let's go to bed," I whispered.

"Yes, please," she replied.

In the bedroom, we stripped each other naked, and I placed her on her front so I could lick all the way from her ears and neck, down her spine, and into her crack. I pushed her buttocks apart and licked her anus. She groaned in dirty euphoria, then pulled her knees up and exposed her arsehole to me. And so I licked this willing student to orgasm via her bottom.

After taking a few moments to compose herself, she pushed me onto my back and began what may or may not have been her first blowjob. Novice or not, she demonstrated what many women don't understand: that the key to giving good oral is to enjoy what you're doing. She sucked me tenderly, thoughtfully and very excitingly. I wondered if she would freak out if I came in her mouth, but I wasn't going to do that anyway. I was going to fuck this girl as I knew she wanted me to.

As I turned Tara over, she came right out with it: "Only if you have a condom."

I reached into the bedside cabinet and pulled out a string of sachets. Tearing one off and open, I handed it to her and knelt like a horny dog in front of her. She took the condom and I could see her working out how to do this before doing it perfectly, sliding the sheath down my hard, eager cock. As a final flourish, she dipped and sucked by rubbery member, before lying down, ready for me.

I parted her legs and made her raise them, exposing herself to me. She looked away in embarrassment before sneaking a quick look at how this man was going to take her. Her arms were above her head as if she were waiting to be pinned down, so I grabbed her wrists and held them as I pressed myself on her and into her. There was a bit of resistance from the ring at her entrance and she gave a quiet cry as I pushed through it. And there it was: she had been a virgin and now she was not a virgin. A look of disbelief gave way to one of relief and then she stared into my eyes as if to say, "Okay, so shag me."

And I did. I shagged this lovely young woman, pushing my cock deep inside her, banging her hard, tickling her bottom with my finger and then shoving it right up her arse. She did the same to me and for a few seconds we were unbalanced as we juggled cock-in-cunt sex with a nasty, dirty, finger-up-bum version. Then we abandoned the digital element and I took her by the shoulders as we pounded at each other and soon she was boiling like a kettle, throbbing inside and squealing as she came.

Then Tara extricated herself from my clutches and pulled the condom off so she could suck my cock.

To use an American expression, she graduated that day. When we left the flat, I felt she had a new way of walking, a new poise, energised by the fact that she felt like a fully qualified sexual woman.