Lord Snowdon - the photographer, designer and one-time brother-in-law to Queen Elizabeth - will go down in social history as a man of monumental, mythical charm. A male interviewer once declared him more charming than Bill Clinton and Hugh Grant; a female interviewer described him as so charming he was "untouchable".

It is a reputation he has been saddled with since the 1950s, when he first waltzed out as a Debs' Delight.

Now 73, his charm is shot through with vulnerability. His voice is faltering and soft, and he punctuates his sentences with long pauses, at times chuckling like a schoolboy, at others looking unreachably melancholy. He is handsome, but so slight he seems swamped by his college-style clothes - black trainers, white T-shirt, cotton trousers and pink socks.

In his nightclub days he was famously well dressed, but he claims not to have had a suit made since leaving Eton."I'm very lucky, because I'm an off-the-peg size."

Snowdon repeatedly describes himself as "lucky", though in some ways he is not. He contracted polio at 16 and the resulting lameness has recently become more pronounced. Snowdon may be infirm but his upper lip is stiffer than a cardboard box.

He dismisses his polio as "boring", stressing how lucky he was as a teenager to have his hospital bedside enlivened by amusing visitors. "Noel [Coward] came to see me, and so did Marlene Dietrich," he says. "They were awfully nice." Did they perform for him? "Do you know," he says, "I can't remember."

However, plenty of women have loved him - most famously Princess Margaret, whom he married in 1960 after courting her in a shared-bathroom flat in East London where they ate fish and chips from the wrapper. There is a formal photograph of her on the desk behind him. He has never talked about her.

But did marriage into the royal family influence his career as a photographer, which by then was already well established? "Didn't affect it at all." Are royal sitters any different from non-royal ones? "Not at all. People are people."

Snowdon has immortalised thousands of them. He began at Eton, where he revived the school photographic society. After half a century his portfolio contains many mighty names - Sir Alec Guinness, Sir John Gielgud, Jack Nicholson, Lord Laurence Olivier - but he seems uninterested in discussing them. He concedes that the painter Francis Bacon was "rather frightening" but was rather less impressed with the singer Macy Gray.

"She arrived two hours late, which I think is rather boring, and she didn't say hello. She just walked into the studio and picked up some grapes. Then she disappeared to go shopping. I only took three photographs."

As a photographer he likes to be called simply Snowdon ("Anthony Armstrong-Jones always sounded a bit too long"), yet he is not coy about his provenance. His family crest is everywhere: etched into the glass coffee table, engraved on the silver hairbrushes in the lavatory, on his cuffs and his signet ring and even stamped on his Filofax. Snowdon is steeped in the upper-class tradition of not taking anything too seriously, which probably explains why he is dismissive of his trade.

"Photography is not art," he unhesitatingly says. "It's mechanics. It's to do with pressing buttons. A lot of people of my generation took it up because they couldn't draw."

He believes that photography today has become "too grand": "When I'm taking a photograph, I try to be like a chameleon. The photographer is not the important thing; he should be invisible. If you have a recognisable style, it's very limiting."

He insists, however, that his eldest son, furniture-maker David Linley, has surpassed him on every artistic front. "He's a real carpenter, but I'm simply a jerry-builder," he says. "I'm terribly proud of what he does. I love him to death - I talk to him every day on the telephone. Sometimes I worry that I love him too much."

It has been suggested that he is more suited to being a father than a husband (he has been divorced twice). His West London house hints at parental devotion. On the kitchen door there is a childhood growth chart featuring the progress of David and "Ya Ya" - his nickname for his daughter, Lady Sarah Chatto. The study is cluttered with black-and-white photographs of them as infants, one or two with the Queen Mother. Was she a good grandmother? "Delightful, absolutely wonderful. I was a huge fan."

In 1978, after his divorce from Princess Margaret, he married Lucy Lindsay-Hogg, to whom he has a 23-year-old daughter, Frances. "She's just published her first photographs," he says, handing me a brochure of fashion pictures and pointing to the credits on the cover.

His second marriage collapsed a few years ago after he acquired a son, Jasper, now five, from his much-publicised romance with Melanie Cable-Alexander, a journalist whom he met while guest-editing an edition of Country Life. She once complained to Hello! magazine that Snowdon had never visited his son. Has he since made contact?

"Yes, I do see him," he says, then suddenly checks himself. "Right! What's next?"

One of the curious things about Snowdon is that he agrees to talk with journalists. Surely the interviews get irksome - but perhaps not, for having begun his stage career aged five as Peter Pan, Snowdon clearly likes an audience. "I like make-believe. I made my own costume out of laurel leaves," he said.

Though Snowdon says he no longer identifies with Peter Pan, does he fear getting old? Snowdon giggles: "Getting old? Surely you mean getting older? No. I think I've had a jolly good innings, really."

Telegraph, London

                                                                    ******************

The unrepentant lothario: Lord Snowdon and his insatiable appetite for sex

Just after Christmas 1996, Tony Snowdon phoned his secret lover of 20 years, Ann Hills, announcing himself as usual by a coded name in case anyone was listening in.

He was responding to a message from her, but she did not pick up and so he left one of his own: he would love to see her over the holiday period, but it was not possible. He ended: 'Chin up!'

The new year began, and Lucy, Tony's wife, was at their home in Launceston Place, Kensington, waiting to leave for the airport; she was off on holiday to India.

The bell rang, and she opened the door, thinking it was the taxi she had ordered. A man stepped forward and said: 'I need to speak rather urgently with Lord Snowdon.'

Tony was downstairs in his studio as usual. Lucy called him, her taxi arrived and she left, leaving Tony with the visitor.

The man came to the point: he was a newspaper reporter, Ann Hills was dead  -  she had killed herself  -  and he had learned of the message left on her answering machine.

A deeply shocked and distressed Tony told the reporter: 'Ann was terribly nice and great fun. I never thought she would take her own life. I've seen her on and off over the years and never talked about her private life at all.'

When the reporter told him that his paper was aware of his long sexual relationship with Ann, he put his hand up to his face and said only, 'Uh-huh. I'm not going to elaborate on this at all.

She was a friend and it's a very, very sad incident.'

But the reality was that he had been sleeping with her since the day in 1977 when she brazenly turned up on his doorstep and said she wanted to have an affair with him.

This was after his separation from Princess Margaret but before his marriage to Lucy.

Throughout his marriage, Tony and Ann saw each other regularly, and always in the greatest of secrecy.

Though she had other lovers, Tony was always her priority, and, as the years went by, she longed for more openness and a greater commitment from him.

But latterly, her life had gone into a downward spiral.

She worked as a freelance journalist but had been sacked from a longstanding column in The Guardian.

A live-in lover had broken up with her because she could not give him children, and her latest relationship was falling apart.

She was 55 and hated the prospect of a dwindling succession of lovers as she aged.

As for Tony, she told a friend: 'I'm feeling really p***ed off about this affair.

At the best of times I don't see him nearly enough. And at Christmas, naturally, he's got to be with his family.'

Her Christmas was spent with her ex-husband and their grownup children.

Then on December 29 she took her elderly father to the theatre.

He was aware that his daughter's self-esteem was at rock bottom.

'She could not face not being a success at journalism,' he said.

'She also worried about the prospect of not having a man in her home.'

It was then that, desperately lonely, she rang asking Tony to call her, which he did  -  although no one knows if she ever actually picked up his last message.

On New Year's Eve, a friend rang to invite Ann over, got her answering machine and felt worried.

She contacted Ann's father and together they went round to her mansion-block flat in Marylebone.

On the kitchen table was a suicide note, telling of her problems and asking for a brooch Tony had given her to be given back to him, along with a note saying that she loved him.

There was no sign of Ann, however, until her father went out on to the flat's extensive roof terrace.

It was a freezing night with a sprinkling of snow.

Ann's body was in a far corner by a chimney-stack, wearing a black dress and the stiletto heels she always wore to add height to her doll-like frame.

Beside her lay an empty bottle of Moet et Chandon champagne and a china mug lined with the sediment of the massive dose of tranquillisers and pain killer that had killed her.

The police took away her diaries, and from these it was clear that the taking of her life was no spur-of-the-moment decision.

She had always seen suicide as a way out. Six months earlier she had made a will and put all her affairs in order, but those who knew her were sure that nothing in her relationship with Tony, who had always been supportive of her, could have triggered her tragic end.

At the inquest, notes from her diaries were read, revealing not only her tangled love life but also her deep feelings for Snowdon. 

The Press had a field day with the story.

In India, Lucy picked up an English newspaper to learn that her husband had had a mistress for the whole of their married life  -  and before.

It was a bombshell, and deeply wounding for her. Nor, on her return home, did Tony, who hated discussions of this kind, give her any sort of explanation.

But worse was to come. 'Most people in Tony's life don't know what's going on in other areas,' one of his assistants once told me.

'He is brilliant at keeping a lot of balls in the air at once  -  but sometimes, they all crash. And then there's massive fallout.' It was about to be one of those moments.

Tony had been at a party to mark the centenary of the magazine Country Life. Its features editor was a young woman by the name of Melanie Cable-Alexander. Tony spotted her across the room and asked to be introduced. His interest in her was obvious; she was to be his nemesis.

Melanie, daughter of a baronet, was a stylish, intelligent and attractive woman of 33  -  the same age as Tony's daughter Sarah. Tall and slim, with an excellent figure, she had a warm, open, sexy manner about her.

Country Life had invited various eminent people to guestedit one of its weekly issues, and Tony, with his knowledge of photography and layouts, was a natural choice. Melanie was delegated to work alongside him.

She felt an immediate sense of rapport with this good-looking older man sparkling with ideas and fun. As she lived in a flat only a few minutes' walk from Launceston Place, it was convenient for her to drop by on the way to work if there was anything that needed discussing.

He signed his faxes to her 'Snowdrop' and called her ' Darling Melanie' but the idea of an affair never entered her head. He was twice her age and married.

He invited her to Old House, his much-loved country retreat in Sussex, and she had a pleasant lunch there with Tony, Lucy and their daughter Frances. But the next time he asked her down there, they were alone and he made it clear how attracted to her he was.

A serious affair started, largely conducted at Old House, where friends treated them as a couple. Melanie was now deeply in love.

It was a shock for her to discover she was pregnant. It was 'a mistake', she said later and she would be bitterly hurt by suggestions from some of Tony's friends that she had tried to trap him into marriage.

Nervously she broke the news to Tony, uncertain of what his reaction would be. It was all she could have hoped. He said it was entirely her decision as to whether or not she had the baby; if she decided to, he would stand by her.

She didn't know what to do. She was pregnant by someone extremely well known but who, to preserve his marriage, insisted on secrecy.

What would be the effect on a child growing up with a Father who could not be acknowledged? She had no real home and not much money.

Could she work and look after a child on her own? She tried discussing all this with Tony but it was the sort of conversation he simply would not have.

Eventually she decided that the opportunity to have a child by someone she loved overrode all other considerations. She would go ahead and accept the consequences.

As her pregnancy became more obvious, one of her visits to Launceston Place prompted Lucy to ask Tony who the father was.

'Oh, some man. . .,' he replied vaguely. 'I think she had a onenight stand.' Lucy, who after the Ann Hills affair had realised just how practised her husband was at concealing the truth, was not convinced.

For her part, Melanie had been telling him he should tell Lucy the truth.

If he wanted his marriage to work, as he said he did, he should face square-on what was happening. But instead he began to insinuate that perhaps the baby wasn't his after all. Melanie was devastated at the implication.

Tony, either unconvinced about the paternity or hoping against hope, said they had better have DNA tests.

These were done and proved without a shred of doubt that he was the father.

One evening soon after the test results came back, Tony telephoned Melanie, and, instead of talking himself, put Lucy on the phone.

She asked if the child Melanie was carrying was Tony's. 'I'm afraid it is,' replied Melanie. 'Thank you very much,' said Lucy politely. 'I just wanted to know the truth.'

Lucy's love for Tony had been wholehearted and she had vowed that she would never leave him and never cause him to feel rejected. But now she felt utterly betrayed.

The dagger in her heart was that he had 'not been straight' with her. She moved out of Launceston Place.

Two weeks later, on April 30, 1998, Melanie's son Jasper was born. Tony's name was not on the birth certificate, and his involvement was not yet suspected. But gradually rumours began to spread.

Melanie noticed she was being followed by journalists. One day Tony arrived to find Melanie and two photographers waiting outside the door. The story was out.

With Lucy gone, Melanie and Tony could see each other more easily, and they did so. For Tony, sex, as always, was a motivating force.

But at the same time, he was desperately trying to patch up his marriage. He could not, however, bring himself to do the one thing Lucy wanted  -  answer all her questions truthfully.

His life at this point was dismal. Melanie came round when she could, but most of her time was occupied by her job and her growing child.

For the first time in many years, Tony, who hated being on his own, spent much of his time completely alone. He seemed low and depressed.

His lifeline was his work, but even here there were disappointments.

In early 1997, not long before the death of Diana, Princess of Wales, he had taken the catalogue pictures of her for a charity sale of her dresses  -  only for them to be judged too formal alongside the fresher, livelier pictures taken to promote the sale by the new star photographer, Mario Testino, whose pictures received all the media attention.

It felt like a snub for Snowdon.

Meanwhile, Melanie was struggling for money. She had no home of her own and was living with a small child in one room of a friend's house. There were confrontations over how much support Tony should provide.

She had refused offers from various newspapers to tell her story, but Tony asked her to accept a lucrative offer from Hello! to finance a house for her. She was unhappy at the idea but consented.

The interview made two things absolutely clear: that she, and she alone, would be bringing up Jasper ('he's a Cable-Alexander and not an Armstrong-Jones and that's final') and that Tony was a largely absentee father.

When asked how often he came to visit his son, she replied: 'He has never visited Jasper. He has seen him on a few occasions, though, when I've been out pushing the pram.' The feature brought in £250,000, which paid for half a flat in Kensington. Tony stumped up the rest.

As their affair continued, Melanie found that its drawbacks were beginning to outweigh the positive aspects. Tony was controlling and over-possessive of her time  -  something difficult to incorporate into life with a small child. He was also too demanding sexually, with a libido higher than men half his age.

Although Lucy was long gone from Launceston Place, Tony was still hoping for her return, and there was no question of Melanie and Jasper moving in.

The three of them did, however, spend weekends at Old House.

But Tony, with his low boredom threshold and his preference for being the main focus of attention, lacked the patience necessary to establish any kind of bond with his growing son.

He also disliked a two-year-old claiming most of its mother's attention.

He was used to having everything around him arranged in its special place, and to have a tiny child roaming free was like having a tiger in his home.

He would try to discipline Jasper in a way Melanie did not approve of.

Back in London, Melanie still called at Launceston Place on her way back from work before dashing home to release Jasper's childminder.

It was an exhausting routine. The affair began to crumble as Melanie realised there was no future with Tony.

Tony's hopes of a reconciliation with Lucy were dashed when she filed for divorce and was granted one. Yet neither she nor Tony pushed for the decree nisi to be made absolute.

This nourished a faint glimmer for him that he might still get her back.

From then on, if a newspaper referred to him as being divorced, he would write immediately to point out that, actually, he was still married.

Lucy and Melanie had now both departed but he was not alone for long.

Old girlfriends came to lunch; once or twice strange girls were spotted under the duvet by his housekeeper when she went up to make his bed.

And a new regular lover appeared  -  brigadier's daughter Emmy Hirst, who was slim, blonde, elegant and beautiful. She was a friend from way back and when he moved the relationship up a gear, it seemed perfectly natural to both of them.

By now, Tony  -  unrelenting champion of the disabled who had used money from his divorce settlement from Princess Margaret to establish the Snowdon Award Scheme to give grants to handicapped students - was very much disabled himself.

The effects of his childhood polio returned, causing muscular atrophy.

From limping badly and using a stick, he now needed a wheelchair.

But no one ever heard the mildest word of complaint from him.

For Emmy, it was sad seeing someone who had been so active now confined for most of the day to a swivel chair in front of his desk.

She admired his courage, and she was balm to his spirit.

He was still a big earner  -  he charged  £2,500 for a portrait and his annual earnings were upwards of £250,000.

But savings would have to be made. There were financial complications in his life.

With a wife living separately, their daughter, and his son by another woman to support, the bills were piling up. With a heavy heart, he sold his beloved Old House.

Then businesswoman Victoria Charlton, another old friend, came to work for him.

Victoria found him new and lucrative clients among Russia's billionaires. She took him on a photographic tour of India with her, which for him felt like a return to the golden days when he flew all over the world on exciting commissions.

They began an affair. For a long time, Emmy was unaware of it.

When Emmy cottoned on, she left.

She had been with him for 31/2 years and did not see why she should put up with infidelity from someone for whom she had done so much. 'I'm into caring,' she told him, 'but not into sharing.'

However, what neither Emmy nor Victoria knew was that Tony had taken yet another old friend as a lover. Marjorie Wallace, chief executive of SANE, the mental health charity she founded, had known Tony since she was a journalist accompanying him on photographic assignments at the Sunday Times back in the Seventies.

They went out on the road together for anything up to a fortnight working on stories about conditions in hospitals and mental homes.

Many of these assignments fell to her because plenty of her colleagues found Tony difficult to work with.

And Marjorie soon discovered why. 'He would insist on being incognito, so I would ring up the hotel and tell them to expect Miss Wallace and Mr Smith.

Then we would arrive and if they didn't recognise him, his face was a study.' He would sign in with a huge, flourishing 'Snowdon'.

In the car, he would always insist on having the window open, even when rain was coming in. 'Could we have the window up, Tony?' Marjorie asked once, with water pouring down her shoulder.

'But if I close it, how on earth will they recognise me?' answered a surprised Tony.

She found Tony  -  as so many did  -  fascinating, endearing and maddening.

And this is where he is now, a man in his late 70s who has two regular mistresses and still flirts with everyone from women to waiters.

The physical horizons of his life have shrunk. Scarcely able to walk, he sits for most of the time in a swivel chair beside his desk, which is covered with photographs from the past.

Pride of place goes to the image of a young, exquisite Margaret.

Her death in 2002 after a series of strokes deeply upset him.

At one stage in her declining years she had refused to take his calls and expressed the mistaken view that his treatment of her had somehow precipitated her illness.

And towards the end, she refused all male visitors, including him. 'I look so awful now,' she said. 'I don't want them to remember me like this.'

But Tony does not. These days there is a determined shutting of the mind to unpleasantness, and he views their marriage through ever-rosier spectacles.

The photograph on his desk serves to remind him daily of the beauty, wit, allure and excitement of the girl he fell in love with all those years ago  -  and with whom the name Anthony Armstrong-Jones, Earl Snowdon, for all the trouble in their life together, will always be inextricably linked.

                                                                               ********

Extracted from Snowdon: The Biography by Anne de Courcy published by Weidenfeld & Nicolson on June 12 at £20.