The letter came at just after 11am, which was the time the mail came round in the offices of the Telegraph Magazine, then just off Fleet Street.

When you write for a newspaper or a magazine letters come in various categories: crowing letters ("The capital city of the Treens was Mekonta, I am surprised you didn't know that"), pained letters ("I could see you were scribbling in a notebook, but I did not expect to find myself quoted in a national newspaper"), cross letters ("I take great exception to your references to Carmarthenshire County Council. I assume that at some time you failed to achieve employment by that body"), even the odd fan letter. The last I tended to keep, though in time I usually lost them.

But one letter I have not lost. Immaculately typed on four sheets of A4 paper, and addressed to me at the magazine, it has, however, no home address, just a date: 3 May 1981.

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"Sorry about the lack of tears. I do regret their absence as much as the lack of some emotions which may make me less of a woman. However, I had just undergone the most profoundly moving experience in my recollection. I had been looking forward to 12 hours (was it?) of you, and was utterly relaxed into the safety of this eternity of bliss. You are so thoroughly addictive, and you and your hands and your eyes and your mouth and your tongue and your body had transported me to such realms of ecstasy that I had hitherto neither known nor even believed possible ... "

Eh?

Until then it had been just another office morning. That is to say, at my desk I had been smoking my pipe, reading with some enjoyment the profile of a Welsh tramp I had spent six weeks writing for the magazine (and hoped to spin out for another two), and, with even more enjoyment, watching the strong bare legs of the secretaries as they swore in their precise English upper middle class voices, chewed their long hair, and lied to their boyfriends on the telephone ("What a bore, I can't make tonight, I have to go for drinks at my godmother's"). As far as I was concerned I hoped things might go on like this for ever. This was a colour magazine in the time of its last hurrah, spendthrift, mad and confident, before the advertising revenues faltered, and the accountants came like the barbarians. It was a time of fantasy. And then at 11 o'clock on a May morning the letter came. I read on, as I am reading it now. The letter is yellowing and creased, but then I have been reading it over and over for 28 years.

"On Thursday came the pain, and no hangover to cover it with. I got up and dressed and people came to sit with me like you give your company to the bereaved to alleviate their grief or perhaps to hear something awful that may brighten by comparison your own life. I don't know because I could not talk and I could not cry, and I was left locked in my own personal Hell.

"When I found myself alone I climbed the stairs to our bed. I had not washed and I would not change the sheets I had lain on with you. Besides, rising at all had taken all the resolve of which I was capable. I sank on to the bed, taking care to land where your body had been, and froze into a paralysed state, lamely thinking, if this is death, what has broken since it could not have been my heart? I was so cold and could not move to switch on the electric blanket. Then I was suddenly hot as in a fever, and the centre of my body ached as if the emptiness were growing to fill me to the outer limits of my skin, and, ever growing, was about to tear me apart. Every muscle ached for you, and all of me was burning for your touch. Then those rich juices of love that were longing to mingle with yours came pouring out of my ..."

I held the letter up to the window, but, no, I hadn't made a mistake.

At that point I put it down, for despite its wordiness the prose had an intensity you tended not to get on colour magazines. Was the writer a lunatic? After 10 years on the Telegraph I thought I knew all that was to be known about lunatics. The Magazine appeared inside the main paper, but was in it, not of it, rather like Montenegro, the independent little mountain kingdom that somehow survived inside the ramshackle Ottoman Empire, a place where the central authorities never came. It – the magazine, that is – had its own offices away from the main building, rooms here and there, the centre of its power seven floors up from the department where I lurked.

If you were in favour, you could go anywhere you wanted: in my case Greenland, where a slipstream of farts from dog teams, fed on fish, hung in the thin Arctic air, 10 straining rumps pointed at the sleigh; or the world's one nudist city, where the dress shops were a scrum of naked women, the bank a queue of creased buttocks waiting to change its Deutschmarks, and from which, emerging into the outside world after three days, I felt my heart pound at the sight of a woman in a dress. Anyone you wanted to meet you could, which for me meant Helen Mirren, a retired hangman and the men who had written the comics and the radio serials of my childhood. It also meant the historian A.L.Rowse, who scuttled by to kneel behind me on the floor when I entered his rooms in All Souls and asked, still on his knees, "You a hetero?" I said I supposed I was, but that I had never really thought about it. "Knew it, knew it," he said triumphantly. "Knew you were heterosexual as soon as you scuffed my mat, and didn't straighten it." And it meant Margaret, Duchess of Argyll, who, after reading what I wrote about her, got an injunction on the whole magazine which would have cost the Telegraph hundreds of thousands of pounds, had it not been lifted at the very last minute. After 10 years on the magazine I hadn't thought anything could surprise me again.

But by God it did.

Like a tank, the relentless eroticism was trundling on.

"Nothing that I had hitherto decreed I would or wouldn't do was under consideration. I stripped my clothes off, still laying (sic) on my belly. When I got to my panties I could nearly hear you and feel your hands that are as soft and gentle as mine. My fingers had to find the hard and throbbing point. The touch that could have been yours released new floods and a torrent of ecstasy and pain. When I turned to lay (sic) on my back I was empty and so alone. I began to hope that everything would go away: the emptiness, the need for you, the longing and the memory. If I were to go crazy, how would any alternative matter? If you had telephoned me then, I would have asked what I could do just to hear the sound of your voice, and I would have done anything.

"As you said I would, I MISSED YOU. At that moment my body had nothing to cling to but the memory of you: the electrifying feel of your skin against mine, the ardent desire to touch as much that is you with as much of me as possible to set all the nerve ends tingling, to hear your voice in my ear, breathing words that no one has ever said to me before, to feel and to smell your hair and your skin and to have the glorious freedom to kiss and to lick every part of you.

"I am yours even if I never see you again ... Just now I remembered something else you said. You do have that effect on people. My anxieties seem to have shrunk away as to be barely visible. I have grown and from you or God or somewhere I have got the strength to handle an entirely new order of priorities. Also I love you."

It was signed "Gina". At first I thought it a hoax, but it was too elaborate for that. Hoaxes, like ransom notes, are to the point.

So, whoever Gina was, some experience had hurt her into stately wordiness. Reading it again now, I wonder if English may not have been her first language, for there was the odd spelling mistake and the confusion over "lay" and "lie". Someone had clearly rung all the bells for a very intense woman, religious, lonely, not too cursed with humour, and probably not young. Only I hadn't rung them.

A fortnight later the second letter came, addressed to "Byron Rogers, Telegraph Magazine". It was clear that the writer, like Gina, had no home address for the recipient, and did not give one for herself. It too was neatly typed, though this time just a note. But in other respects it was very different. No mention of feelings this time, or at least none on the surface: whoever she was, the writer was remembering a romp, with three people involved, also a dog in some obscure supporting role.

"You never told me you wrote for The Guardian as well, you cheeky devil ... "

I had written a short feature the paper had headlined "Here's to You, Mrs Robinson". This had been prompted by a court case involving a rather good-looking woman in her thirties, living somewhere in the Home Counties, who for some years had housed French teenage boys on school visits, then seduced them. Most had welcomed the experience (according to one of their teachers the essays they wrote about their holidays were effusive, though vague), but it all ended abruptly when the latest two rejected her advances, running into the street and bawling in their best English for, of all things, an ambulance. The judge gave her 18 months. He also called her "an evil woman", which I thought dreadful, considering that I, possibly he, and just about every other man had spent our teenage years waiting for something like that to happen to us. My feature brought down the wrath of the paper's feminist readers upon me, and I had a whole indignant section of the letters page to myself.

But this letter-writer hadn't seen it like that.

"You have got a lot of strings to your bow – as we all know! Sandra said the article should have been titled ROGERS ON FUCKS AND HOW TO GET THEM. And what about Helen Mirren last week? I bet you charmed the pants off her too – coming off all bashful and on the edge of your seat."

That had been a feature interview, after which Miss Mirren had seen me off into the night, wobbling on my bicycle, with the remains of a bottle of whisky, most of which I and her then boyfriend Liam Neeson had consumed between us. I fell off the bike in Grosvenor Square and, unhurt, finished off the whisky at the kerbside. There followed two lost hours, during which my girlfriend, later my wife, went to the police, who thought it no end of a joke, and suggested I might have gone to some nightclub with Miss Mirren. Which set her mind at rest no end.

"I'm sorry I have got in touch with you again after 'that night'. I know I promised not to but I just keep thinking about it all the time and deep down Angie feels the same. She hasn't mentioned a thing but I look at her across the pool and she's got a funny smirk on her face. She was very upset about Steve coming back, she promised that he never comes back from the Scottish trips earlier than three days. Honest! Anyway he's such an idle sod he didn't think there was anything funny about me and her starkers and playing with her daft dog! Not so daft if you ask me. I think he was pissed anyway – Steve, that is. You got back alright I hope, round the back. I know you were upset but we promise it won't happen again, so if you want to see teeny-weeny me and Angie again you'll know where to find us on Thursdays. Please, please ...

Gilly. X X X. "

So: a typist this time (Gina had not mentioned jobs, and no locations apart from bed), and a good-time girl who every Thursday went on the town with a married friend from her office. But again she was writing to a sexual athlete who had appeared in her life like Spring-heeled Jack, then disappeared – though, again, Gilly had been told this would happen.

Everyone I talked to about it (which was just about everyone I met) thought it hilarious, but I began to get worried. What would Jack do next? The next thing was a postcard addressed "To the town's Handsomest, Sexiest, most sought after Lover Boy." On it this was written in a large, wild hand, "S.O.B.'s presence is requested at a private dinner to be held at a venue yet to be arranged in aid of the 'Misfits of the World'. Dress optional. RSVP. E.B."

So: another disappearance, more bells having been rung, which clearly now hung idle. I decided to see the police at this stage, who also thought it a joke.

"Try to see our point of view, say we got him, what could we charge him with?" asked a detective sergeant at West End Central. "I mean, all he's ever done is go to bed with women. And their only regret is that he's stopped doing it. The only complainant is you."

As I was leaving he said idly: "Just one question, sir. Have you any idea why he should want to pretend he was you?" I said I hadn't, but as I went through the door I realised I hadn't quite liked the way he had asked that.

Still, his question was partly answered when the first phone call came. It was from a woman who wanted to know why I hadn't turned up at the weekend. She wasn't cross, she said she quite understood if I'd been sent abroad at short notice or something; she just wished I could have let her know.

I explained things to her, and there was this long silence. I asked where she'd met him, and she said at an afternoon dance at the Leicester Square ballroom, when he'd told her he was an international correspondent who was abroad most of the time, living out of a suitcase when he was in this country.

She then started to cry, and there was a click as the phone went dead.

So that was it.

It was quite smart then to say you worked for a colour magazine, and of course it was the perfect cover, particularly if whoever you told knew little about journalism. And I don't suppose anyone who turned up at an afternoon dance was going to ask too many questions. No address, no phone number, just Captain America coming and going, and out of reach of these vulnerable women, as I had now come to assume they were.

Suddenly it had become sad.

There were other phone calls which I managed to avoid. ("It's a Mrs Rowlands, says it's urgent.") But then one got through, and this time there were no tears. I went round to see a divorcée in her late fifties, living alone in a council flat 12 storeys up in a tower block above Hampstead, who was more annoyed than upset. ("Ooh, the bugger.")

She too had met him at a tea dance, for there was one thing about such places, she said, they did allow one to meet people, and she coloured slightly at this, implying the word covered a great deal. Her children having left home, she had begun to find life lonely.

Of course, I thought, tea dances, afternoon ballrooms: the perfect hunting ground for a sexual predator, the women would be of a certain age, and lonely. "And they're that surprised," a sergeant in the Scotch Guards who had stalked them in such places told a friend of mine, "they put their hearts and their airses into it."

My hostess made tea. She was a rather nice, well made-up woman with little ladylike ways (after the "bugger" she had said, "I don't know what made me say that"), but there was a toughness there. She said that if he got in touch again she would ask him round, and, if she could get him off-guard, would take a photograph of him, which she would send me.

She showed me a poem he had written, addressed to her. It was, and is (for I still have this too), in sloping capitals:

"Lately my life has lacked the light/ Until you came, a star so bright/ Your very nearness warms my heart/ Once more my life begins to start/ Your happy bubbling ever effervesence (sic)/ Warms – draws me to your prescence (sic)."

She gave this to me, saying she didn't want to see it again. Seduction is one thing; poetry, however bad, hurts.

A fortnight later she phoned to say she had the photograph. Caught in flashlight, a man, leaning on a door frame, is grinning at the camera. He is thin, pale, not bad looking, but with the sort of eye-teeth for which Christopher Lee needed a make-up artist: they are the very long, white teeth of a vampire. But what had made her cross, she said, was how perfectly at ease "the creature" had been.

"I know who asked you to do this."

"Yes, and he's getting a print."

"Poor old Byron, I knew he was after me, but there's nothing at all he can do about it."

Still, it must have worried him, for the letters and the phone calls stopped. But the strangest development of all has just taken place. When I started on what you have been reading I got in touch with a friend of mine to check some of the details; now living in retirement in Cornwall, she was on the magazine with me. A fortnight later she rang me.

"I can hardly believe this, it's the most extraordinary thing. I was telling a lady who's just moved down here from London about that chap who used to pretend he was you, and we were both roaring with laughter when I must have mentioned the name Byron Rogers, for suddenly she stopped laughing. She said, 'Omigod, not him.'

"If it's the same man, in the 1980s her mother had an affair with him. I gather they were all a bit worried at the time. But her mother's coming down at the weekend, I'll ask her."

A few days later she rang again. "It was him. I told the mother your story, and she was startled, for everything checked out. Everything. Her daughter even teased her about whether he'd been a bit of a mover and shaker in the bedroom department, but all the old lady said was, 'Yes.' Perhaps you'd better not bring that up. Oh yes, I forgot, she's agreed to talk to you."

This is her story.

"In the 1980s I was in my fifties, separated from my husband and working as a housekeeper/caretaker in this block of flats in Mayfair. And every Monday night I and some friends used to go dancing at the Café de Paris. Monday night was Ladies' Night. And that's where I met him. He was tall and dark, had prominent teeth, I remember that, and was very likeable. He told me he worked for newspapers. In fact he had a whole briefcase full of his articles – sorry, your articles – for whatever you say about him, he was your number one fan. He must have cut out everything you wrote.

"And even at the beginning that struck me as a bit odd. I didn't know any writers, but I didn't think they carried old articles around with them. Not to dances anyway. God, this makes me sound such a twit. Of course, later you wrote columns, and your photograph began to appear, which would have put a stop to everything. All this is very sad, don't you think? He had this wonderful knowledge of London. We used to go for long walks together. And suddenly there was all this sex. I'm not sure how it started, I mean I'm a bit of a prude and I'd sworn when my marriage broke up that would be it as far as I was concerned, so I was more startled than anything.

"It wasn't as though he was physically attractive, and I always used to put him in the bath beforehand. But the sex was ... amazing. Not that he did anything out of the ordinary, it was just that it was ... that's the only word for it ... amazing.

"The only thing was that at no time did he mention anything to do with writing, and that's when I started to get suspicious. Then he asked me to his flat, which was in Harrow and very small. And there were no books in it, just paintings of animals on black velvet, and the only furniture a crumbling old sofa.

"That's when I confronted him, and he admitted it. Said he was a misfit, that he'd been sexually abused by an aunt when he was a boy. Or so he said. And then he told me that what he really did was manage a bookshop in the Charing Cross Road. The only thing was, there were no books in his flat. That's when I told him to piss off. I mean, even booksellers must read books sometime. It was so sad. And silly.

"I don't think there was any harm in him, but there are people like that, they can't bear to be ordinary. I thought it was all over, and then years later I saw this drawing of a man's face in the Evening Standard. A man's body had been fished out of the Thames, and the police were trying to identify him. And it was him, I'm sure it was him, it was an uncanny likeness. I know I should have gone to a police station, but I couldn't face it somehow. It sounds daft, but I couldn't face getting involved again, even with him dead."

Suddenly it wasn't a matter of women wailing for their demon lover. To have invited her home would have been a major departure for him, so he must have fallen for her in a way he hadn't for any of the others, not one of whom even had his address. It must have been the one time he had stepped out of character, and he, who had stepped in and out of so many lives and disappeared, was himself made to disappear.

Her description of the flat was so vivid, the emptiness of the room, those awful paintings on black velvet, the tigers and elephants you saw for sale in street markets at the time, to which, his briefcase bulging with cuttings (I was churning the stuff out in those days), he came home each night. Well, most nights. And the effect on me was complex.

Shock had long ago given way to irritation, largely at not finding myself centre stage in my own life, but then this too had given way to awe. I suppose I had come to revel in the adventures of my secret sharer, this Mr Hyde of the Tea-dances. For I had never received such letters. I had never had that effect on anyone. And with me partings had always been messy affairs, mostly on station platforms and, once, in the Romano-British section of a research library. And these were partings which were usually reversed a fortnight or so later, which meant there were other station platforms, other libraries.

We had shared so much, he and I, except he got the ecstasy, I got the recriminations. As to the rest, I knew nothing about him, what he did, where he came from (though one of the ladies had mentioned South Africa). To me he was this long peep-show of Gina, of Gilly and Angie (and why had the husband not been surprised to come on the two of them naked with the dog?) and the others, only they disappeared as I approached the glass, and there was just me peering in.

When someone steals your credit card, and you need to check your statements, you are confronted by the patterns of your spending. But when someone steals your identity you are confronted by that identity as you find yourself staring at it – and in this case not alone but in company.

"Just one thing, sir, have you any idea why he should want to pretend hewas you?" ...

And something I have forgotten to mention. The evening I went round to collect the photograph from the lady in the Hampstead tower block, I asked her, "What's he like? Is he anything like me at all?"

She hesitated for a moment. "No, he's nothing like you at all, dear. I'm not sure how to put this. Well ... he's sophisticated."

But whoever he was, or whatever became of him, because of him I found myself in a film in the production of which I had played no part. And the biggest shock of appearing on screen for the first time, the director Bryan Forbes once told me, is seeing yourself walk away.

It is enough to make a man write his autobiography, if only to reclaim something ...

Adapted from Byron Rogers's autobiography, "Me: the Authorised Biography", published by Aurum at £16.99. To order a copy for the special price of £15.29 (free P&P) call Independent Books Direct on 08700 798 897, or visit www.independentbooksdirect.co.uk