At 48, Theresa Tinggal discovered that she had been adopted as a baby. So began a life-changing - and continuing - search for her birth mother, writes Anne Dempsey

'If anyone reading this letter had a baby girl on June 9th, 1954, in Dublin, I would be grateful if you would get in touch with me. As a mother I know how heartbreaking it must be to have to hand your baby over. However, I fully understand that in the 1950s in Ireland you really had no option. I really just want to find out what happened to you and I hope that you went on to have a happy life."

When Theresa Tinggal wrote this letter recently and sent it to several newspapers she was still in shock. Some months before, at the age of 48, she learnt, quite unexpectedly, that she had been adopted. "I never suspected it, never, even when things were difficult, even when people said I didn't look like the rest of them. After I heard I would get up in the morning look in mirror and ask myself: 'Who am I?' "

She had believed she was Theresa Riney, second daughter of Kathleen and Jimmy, born and reared in Rathfarnham, Dublin, with a younger sister she knew was adopted. "I was very close to my father; he was the one that took me to school. He was full of life and music and fun. But my mother and myself did not get on. I never felt I fitted in and never felt she loved me."

When Theresa was 16 her father died suddenly, and she felt the loss keenly. At 19 she left home for England, the farewell between herself and her mother illustrating their mutual difficulties. "Neither of us shed a tear. I spent my childhood trying to please her, but I could never please her, so at some point I just gave up."

Within a year Theresa was married. "Looking back, I was looking for security, a home of my own. My husband was from Brunei, and things began to go wrong when we left the UK to live there. My daughter Tara had been born, I was a young mother in a foreign country and, while not as strict as Saudi Arabia, life for women was very restricted, and I didn't get the support from him I would have needed to have a freer quality of life."

They had another child, Ryan, but subsequently agreed to separate. Theresa wanted to come home until she found her feet again, but her mother had remarried and moved house, and she indicated that having Theresa to stay for a few months would not suit. "I saw it as yet another rejection."

Theresa settled instead in Bournemouth, on the south coast of England, retrained in IT, found work as a secretary, divorced her husband and made a new life for herself and her children.

"I began again. I made friends; the children were happy. Whenever I thought about my childhood I felt baffled and sad. I stayed close to my younger sister but had little contact with my older sister or mother."

Life would probably have continued on this even keel if Theresa had not met a man. "In January last year I fell in love, really in love. He was an entertainer, great fun. Perhaps he reminded me of my father. But he kept breaking promises to me and finally let me down completely. I became hugely upset, far more than I would have thought. Really I hardly knew this man.

"I realised there was something more to my grief and that every time I was upset it led back to my mother. I decided I needed to go back to Dublin and ask her about my childhood.

"I booked my flight, then phoned her brother, my uncle, and told him what I intended doing. He strongly discouraged me, but I was determined. Some time later he phoned back and said: 'I was sworn to secrecy, but can't go to my grave with this - you are not her daughter.'

I just didn't believe him, so I phoned my older sister, asked her and knew immediately by her response that it was true. My first feeling was one of relief as a big piece of the jigsaw immediately fell into place. But as the truth sank in I became very upset and wanted to know who my mother was."

For the past year Theresa has been piecing her story together. She has heard a lot of it from her adoptive mother, contacted the health authorities and been sleuth-like in following trails to build up a picture of her early history.

"My mother told me that my father expressed an interest in adopting a baby and contacted a social worker attached to one of the maternity hospitals, who arranged de facto adoptions, which I believe were very common in those days," she explains.

"A GP was involved. One of his patients, a young girl, was expecting a baby that June, and when I was born he sent my mother a telegram. Two days later she got a taxi to a house in north Dublin - I know the exact address - and picked me up from a nurse, who gave my mother £45, which was described as a maintenance fee.

"My parents called me Theresa, I was registered in their family name and that was the name on my birth certificate.

"But as you see from this health-board form my real name is Margaret O'Grady. I believe I know my mother's Christian name, but I won't say it publicly, as that wouldn't be fair.

'One of the hardest things to come to terms with is not being told. My adoptive mother says they registered me as their child to protect me, because there was such a stigma regarding illegitimacy in those days. My sisters were told the truth after my father died but say now they had to keep the secret and then there was never a good time to tell me. They find my search difficult and don't seem to understand why I need to do it.

"I just want to find my mother," she says. "I want to find out what happened to her, especially after seeing documentaries about the Magdalen laundries - maybe she was one of those. I just don't know. She may have married, I may have half sisters and brothers. I don't think about finding my father at all, because I had a dad who was everything to me, and I don't need another."

Although her letter to the newspapers brought little response or progress, she says everybody she has been in contact with has been extremely supportive. "I wrote to the address I was taken from when I was two days old and got a reply. The family has been there since 1993 only, but they have given me some leads, which I am now following up.

"I need to find out what happened to my mother. I always celebrated my birthday, but this year there was no celebration. I was really upset. I wondered was she thinking of me. If she was a young girl when I was born she's now only in her late 60s. If I'd known 30 years ago I would have started looking, but maybe it's not too late.

"In an ideal world it would be nice if we met now and got on. But any contact would be good, even if she didn't want to take it any further. When my first child was born I was very happy but sad, too, as I knew what it was like to love your child and realised again what I had lost. Next year I will be 50, and I would love by then to know who I am."

• Theresa Tinggal can be contacted in Bournemouth (00-44-1202-257961), on her mobile (00-44-7884-057826) or by e-mail hineytt@ hotmail.com

• The Irish Adoption Contact Register is a free, voluntary mutual contact reunion registry for those involved on both sides of adoption; more than 1,000 reunions have taken place since 1999. It is administered by Adoption Ireland, The Adopted People's Asociation, 27 Templeview Green, Clare Hall, Dublin 12 (01-4624430). Register information: 01-8674033, www.adoptionireland.com