For Paula used to be Paul, who for over 25 years was married to Karen. They had three healthy children, lived in a beautiful house overlooking a lake, and enjoyed many of the material trappings of the early boom years of Celtic Tiger Ireland. To an outsider, it appeared they had the perfect family life.

But the outwardly successful Paul, in secure employment with a big international company, had a secret that even those closest to him never suspected. He believed he was a woman trapped in a man's body. A vague yearning which at first he struggled to comprehend eventually grew into an overpowering desire to become the person he felt he had always really been.

It was a gradual realisation that ultimately gained irresistible momentum, with enormous personal consequences. He was forced to walk away from his family, home, friends, and well-paid job to live an entirely new life alone in another country.

Paul came to Ireland when his family moved here from Germany in the late 1960s. He was just 17. As a youngster, he found himself inexplicably drawn to secretly trying on his mother's underwear. But his teenage hormones pointed him strongly in the direction of girls. While working as a barman, he met Karen. They became engaged when he was almost 20 and she was 17.

His liking for women's clothes became apparent early in their marriage, though the pair never spoke openly about it. He loved his wife, but he had other deep feelings for which he had no rational explanation. He had the normal sexual urges of a man, but secretly desired to be loved like a woman. He deemed it wise not to mention this to anybody.

They had a son and twin daughters. But he felt he was living under false pretences.

Nowadays Paula Grieg lives in Manchester. She has written a book describing the personal confusion and turmoil which would ultimately lead to a sex change operation. Grieg is a nom-de-plume. Likewise, the names of family and friends have been changed and geographical locations have been blurred to protect those dearest to her. But otherwise the story is told in sometimes graphic detail.

Recalling her growing young family, she says: "I can't say if my urges towards my children were more maternal or paternal, but I knew that I loved them with every heartbeat."

Married life too had its contradictions. " Physically, I was perfectly able to function sexually as a man. But the processes going on in my mind, while doing so, were usually anything but male."

Through the 1990s, business trips abroad gave him the opportunity to explore his secret desires. He took to packing women's clothing. Tentatively, he began to venture out in London and Manchester dressed entirely as a female. He gradually became aware of a whole other world of transsexuals - people who had a sex change. "The trips let me live out my secret life. My children were at home and knew nothing about what I was doing. It was the ultimate deception to them. By this stage, however, Karen was well aware that I packed extra clothes and went out in female mode in the UK," she says.

"By now, things had progressed at home to a stage where Karen had accepted me for what I was and was giving me good advice on what was good on me and what was not, and even letting me have some of her outfits."

But even his wife still didn't suspect the full extent of things. "My internal conflicts were hidden so well from everyone, but they were threatening to tear me and our secure lives apart. The conflict was between the sham 'man' everyone thought they knew and the woman I needed to be," she says.

Counselling in London brought him closer to the path he felt he had to take. At home, things rapidly became more complicated when his son discovered his secret stash of women's clothes. He admitted to the stunned young man what they were for.

By now, the prospect of a sex change was starting to take shape. But this was clearly out of the question in Ireland. He still loved his wife and struggled to keep his family life intact, but this ultimately proved impossible. He went on a last romantic holiday with Karen before starting female hormone therapy.

He wrote an agonising letter to his 17-year-old daughters. This was followed by a "gut-wrenching, heartbreaking, tearful" discussion in which he told them he could only see a meaningful life for himself as a woman. One of the girls left him gutted when she asked: "Who will give me away when I get married?"

He organised a meeting of family and close friends to tell them. Nobody knew what to say. "It was my father-in-law who finally broke the silence. He jumped up, gave me a hug and said that while he could not at all understand what was happening, I had always been a great son-in-law and he could only wish me well for the future." He decided to move to Manchester where there was a support group for transsexuals. His work colleagues had a going-away party for him in the pub, though nobody knew why he was leaving. Despite the heat, he kept his jacket on, terrified they would notice his budding breasts - the result of taking the hormones.

In July 2001, he left home. Five months later, he travelled to Bangkok for 'gender realignment surgery' - the removal of all vestiges of his manhood and remodelling him as a woman. The 11-hour operation also included reducing his Adam's Apple and also breast enhancement surgery.

Now almost 57, Paula says that having a sex change wasn't a lifestyle choice. She admits she has paid an enormous personal price, but suggests the overwhelming need was finally to be true to her real nature. Because Paul retained his German citizenship, the sex change has full legal recognition there. Paula has a new German birth certificate which states that she is now officially female.

Recently, her father's funeral gave her the opportunity to attend the first major family gathering since her operation. She believes it went well. She and Karen spent "quite a while" talking. Her former wife is now in another relationship.

"I spent nearly 30 years of my life with Karen and she obviously meant an enormous amount to me - and still does, " she says.

"By and large, my family have been supportive. My children are great. They have all stayed with me.

" And they have done rather well in spite of the upheavals that they had to go through."

Paula doesn't flinch from the question of her own sexuality now. "The testosterone-driven desire I had for women in the past is now gone, replaced by a womanly desire to be loved simply as a woman.

Dilemma

"As for men, every time I meet someone I like, I am faced with the same dilemma. Do I just let it run, enjoy the moment, or do I disclose my secret at the first possible chance? If I don't, I may have some fun and I may even fall in love. But love is based on trust and trust can't be built on lies."

On the other hand, she says, disclosure will probably cause most men to run, asking "silly questions about their own sexuality".

As for those who know and don't run, she has her own uncertainties. "Do they stay because they truly want Paula, the attractive interesting woman, or do they have some kinky fascination for transsexuals?"

But she stresses: "I absolutely have no regrets. I made the right decisions. If anything, they were made way too late in my life."

Had she embarked on her new life earlier, it might have opened up new romantic possibilities. Does she have a partner now?

"No. I wish I had, but I don't," she replies wistfully. "Love has not come knocking on the door yet. But there's still hope."

No Man's Land: The Story of a Man who Became a Woman, by Paula Grieg, Maverick House, £7.99