I must move on now, Mother. You and most of the family went to the gas chambers, without my knowing.”

“Dear Miss Bechhofer, are you our cousin? If so, are you not one of twins?”

Nearly 40 years separate these two letters. The first was written this year, a letter to a long-dead parent. The second dates from 1988 and was the first indication for Grace Stocken that she was part of a large Jewish family.

For Grace, or Susi Bechhofer as she now calls herself, the traumas of losing her parents and her twin sister, Lotte, has meant her entire life has been a search for identity. In her new book, Rosa, she tells the story of her German-Jewish mother’s tragic love affair with a Wehrmacht soldier, Otto Hald, and the pitiful discovery of letters Rosa had written to her family in America, begging for help to leave Nazi Germany.

As it happens The JC is intimately bound up in Bechhofer’s story, as in 1989, on the 50th anniversary of the Kindertransport, the paper featured the journey of the three-year-old twins, Susi and Lotte, who came from a German orphanage and arrived in Britain in 1939. The girls were adopted by a Baptist minister and his wife, Fred and Audrey Legge, whose first act, bizarrely, was to change Susi and Lotte’s names to Grace and Eunice. Thereafter the Legges did their utmost to erase the twins’ history.

The JC story attracted the attention of many people. One, astonishingly, was Edith Moses, the twins’ former governess, who had looked after the little girls in Berlin and was now living in Bath. The BBC made a film about Bechhofer, and, with the writer Jeremy Joseph, she published a memoir, Rosa’s Child.

There was another, more painful assault on her identity, when the author, WG Sebald, in what turned out to be his final work, appropriated her story for his prize-winning novel, Austerlitz. In correspondence with her before his 2001 death in a car crash in Norfolk, Sebald acknowledged that he had been heavily influenced by her story, but he died before any amendments could be made to new editions of the book.

For Bechhofer, therefore, there was a burning sense of wanting to set things straight. “I wasn’t really able to express my feelings in Rosa’s Child,” she says, “not least because it was written in the third person. I wanted to speak in my own voice, to say something really authoritative.”

In Rosa, she retraces the story of her mother’s doomed romance with Otto, not merely a non-Jew but a member of the Wehrmacht. Both families would have been appalled at the affair, Rosa’s because they were Orthodox Jews, Otto’s because of the increasing legislation for Aryan Germans that forbade any contact with Jews.

By the time the twins were born on May 17, 1936, Otto was out of the picture and Rosa had taken the difficult decision to place her children in a Jewish orphanage in Munich, where they could be well looked after.

She and her sister visited every week, but little Susi had only a vague idea who their mother was. And then it became obvious that there was going to be a war and Rosa — presumably agonised at the idea — sent the girls to Britain on the Kindertransport.

Bechhofer has no memories of the journey to Britain itself. She writes: “The first weeks and months at the manse remain a blank. I know that to accommodate two German-speaking and deprived three-year-olds must have been a serious task. We were under-nourished and suffered from rickets… gradually, memories of Rosa, the orphanage and friends left behind faded altogether.”

Why were the Legges so keen to change the children’s names? Bechhofer sighs. “I’ve given a lot of thought to that. We were two little German girls, and perhaps to be Susi and Lotte [in wartime Britain] might have been a threat. But also, Fred Legge was desperate to have children of his own, and it might have been a way of marking us as if we were their own flesh and blood.” Overnight the children were told that from then on they were to be known as Grace Elizabeth and Eunice May, names taken from the initials of Fred and Audrey’s parents.

Bechhofer didn’t question the name change until years later when she was taking her O levels at school, and was taken aside by the teacher to be told that she had to complete the exam in the name of Susi Bechhofer, and not Grace Legge. It was, she thinks today, a legal requirement, but it came as a huge shock to her, and some of the memories of Germany began to come back.

They were not memories she could share with her twin, because Lotte had become seriously ill. She had developed a brain tumour and eventually died, aged 35, in 1971. 
Much of the book is an attempt to rehabilitate Lotte and honour her memory, as well as that of Rosa.

“Survival”, declares Bechhofer, “is the name of the game.” Throughout her life she has employed a “coping mechanism” to deal with whatever was thrown at her. Lotte’s illness meant a focus on Susi by the fearsome-sounding Fred Legge, whose sexual abuse of his foster-daughter does not find a place in this book. She does, however, refer frequently to his desperate need to control her, from choosing a job for her to trying hard to prevent her from marrying Alan Stocken, whom she met while in her chosen career of nursing.

“This is how I learned to survive, taking everything in my stride,” she says. Today that includes dealing with her husband’s severe dementia; and when she discovered her large, Orthodox Jewish family in New York, dealing with the dismay of her son. 
“I remember when he was 21, hearing him say in our kitchen, ‘I don’t want to know if my grandmother perished in a camp.’”

Frederick, her son, is a composer and church organ scholar, and has now become reconciled to his mother’s background, even writing a musical lament for Rosa.

But the “bullet” which precipitated all this convulsion in Susi’s life was a radio programme on BBC Women’s Hour, an interview with Bertha Leverton who was hoping to arrange a 50th anniversary reunion of the Kinder.

The two women made contact and Leverton then went to Israel, where she made another plea on Kol Israel radio for former Kinder to come to the reunion.

On October 17 1988, Jerry Bechhofer, alerted by the Kol Israel programme, wrote to Susi from New York. In a few short sentences he explained what had happened to Rosa: “Your mother, if she was that, was the next-to-youngest sister of 13 siblings. Two brothers died young. Seven sisters, including your mother, perished in the Holocaust, one sister survived and died here approximately 15 years ago. My father and his remaining two brothers died here, the last — Isaac — approximately 12 years ago.”

Jerry was her first cousin, and in Rosa Bechhofer writes of the mixed pain and pleasure of meeting her Jewish family in New York in 1989. They were warm and welcoming —“My, did they talk!” she writes — but even though she was happy to find her relations, despite their urging she could not re-embrace her Jewish identity. “It was too late”, she says, but she did find comfort in her local church.

On a visit in 2004 her cousin Senta handed her a package of letters that had lain, untouched, in a Manhattan kitchen drawer for more than 70 years. They were from Rosa to the Bechhofer family, pleading for an affidavit that would allow her to leave Nazi Germany.

The letters were never answered and Rosa died in Auschwitz in 1943. It was a painful discovery. “You know, Rosa,” muses Susi, “we must have been a blot on their landscape because my father was German and you had your twins and were not married…The contents of these letters have been a family secret for all these years.”

Not many people could forgive such a passive betrayal. But Bechhofer, who retrained as a psychologist, is accepting. “I wrote the book to reclaim Rosa, to pay tribute to her, the Bechhofer family and my Jewish heritage,” she says.

In that aim, she has certainly succeeded.

Rosa is published by Christians Aware (£9.00)