The daughter of Jewish theatre director William Diamant and his actress wife Peggy, Kathi had spent much of her childhood in Germany, where her father ran the Frankfurt Playhouse, founded by the American government under the post-war Marshall Plan.

After short spells in France and Korea, the family returned to their native America where Kathi went to university, majoring in art.

She chose the German class as an easy option because of her knowledge of German from her childhood.

The 19-year-old had a crush on her German teacher who had chosen a passage from Franz Kafka's Metamorphosis for the lesson.

In the middle of this class, the teacher asked Kathi if she was related to Dora Diamant, Kafka's last love in whose arms he had died in 1924.

Kathi recalled: "The teacher wrote her name on the blackboard. It was my surname.

"I was thrilled that my teacher was talking to me. I really wanted to get that answer for him. It's possible that without that teacher asking me that question, my life would have taken a complete different tack."

Kathi, who now lectures on Kafka, said: "At that point I did not love Kafka. I didn't get it. I didn't understand what I was reading.

"Had I not been asked that question my relationship with Kafka would have atrophied. It was Dora and my search for her which kept bringing me back to Kafka. It was as if she were saying to me, take another look at Kafka."

She continued: "That day I went to the library and looked up everything I could find on Dora.

"She did appear in the final chapters of Kafka's biographies, but nobody knew what happened to her. She disappeared after Kafka's death in 1924.

"There was no record of her except to say that she burned his work. That was Dora's legacy."

Kafka, who died in a sanatorium near Vienna at the age of 40, had given strict instructions that his unfinished work should be burned after his death.

But his friend and biographer Max Brod wanted to preserve his manuscripts, letters and notebooks for posterity.

Kathi later discovered that Dora had indeed, after burning some material in front of the dying man, secretly kept his papers only to have them later stolen by the Nazis in Berlin.

From that day, for the rest of her life, Kathi became inextricably linked with the woman who had shared her surname.

She said: "Dora and I were clearly connected, besides the fact that we shared the same surname. I was born on May 15, 1952, three months to the day before Dora died on August 15.

According to the Kafka biographies, Dora was a 19-year-old woman when she met Kafka in the last year of his life. I was 19 when I first learned about her. That connected us."

Although, after years of search, Kathi never found any genealogical connections between her father's family and that of Dora's, that ceased to matter.

Kathi told me: "What happened along the way about me knowing about Dora was that it ceased to matter whether or not we were related. We were clearly connected. In writing her biography it was better not to be related.

"Through my three-decade journey, inexplicable coincidences made me believe that I was doing what I needed to do and that I was being given lovely gifts of coincidences along the way to keep me engaged on her trail.

"What happened to her was like a Nancy Drew mystery. I needed to solve the mystery. For 13 years until I began my search for Dora in earnest, she just sort of infiltrated me.

"I never forgot her. Everything I read about her was amazing. I wanted to be related to her."

Kathi, who went on from Georgia University to study performing arts at Florida State University and then had an extremely successful career as a TV producer and presenter, later discovered that Dora was herself an actress, joining the communist theatre company Agitprop to campaign against the Nazi regime in 1930s Berlin.

Kathi told me: "Many coincidences kept me going through the long slog.

"It wasn't till 2001 that I found myself in Dusseldorf where she had gone to theatre school. I went to the theatre museum, which had all the letters and records about her theatrical training. Her training schedule was exactly the same as mine."

Besides these amazing similarities, what was it about Dora that made Kathi so fascinated by her and, in fact, use her as a role model?

Kathi said: "Max Brod and other biographers described her as passionate, intelligent and beautiful, the woman who gave Kafka the happiest year of his life.

"I was stunned by someone of my age giving this literary genius happiness.

"Before I began my research in earnest I spent 13 years thinking about her, like what would Dora do in this situation? What would a brave, courageous, intelligent, compassionate, loving, humane person do?

"In that way she began to influence me and my decisions. She has been part of my life since I was 19."

Kathi was also struck by the fact that Dora and the dying Kafka had wanted to emigrate to pre-state Israel and that after his death Dora had tried to fulfil her late Jewish lover's wishes by settling in Israel, but had been called back to her home, which was then in London, when her daughter Marianne became ill.

It took 13 years from first hearing the mention of Dora's name until Kathi was able to begin her search and fill in all the gaps of history, not only about Dora's life, but also about that of her former Jewish lover Kafka.

Kathi was interviewing the curator of the Smithsonian Institution in Washington DC, who was bringing an exhibition of Judaic treasures from the Czechoslovak State Collections, called 'Our Precious Legacy', to San Diego.

The exhibition showed items that had been collected by the Nazis for a Jewish museum they were planning to build to an extinct race.

One of the exhibits was a photographic blow-up of a portion of the Pinkas Synagogue in Prague with the names of more than 77,000 Jews who had died in Bohemia and Moravia.

In the middle of the photographic enlargement was the surname Diamant. The following year, in 1985, Kathi went to Prague on her first mission to find Dora, and also in search of the missing Kafka documents, which had been looted by the Nazis.

Kathi said: "I went to Prague and Vienna, where Kafka died. I was able to visit the room where he died in Dora's arms.

"Then I went on to Israel because I learned that there was a Diamant collection at Hebrew University with the genealogy of 300 different Diamant families. It was boots on the ground. I showed up.

"In 1990, I went to London to find Dora's grave. I stayed for six weeks till I found it, walking miles through very Orthodox Jewish cemetery in the area."

Eventually, Kathi found Dora's unmarked grave in East Ham Cemetery, London. When she told Dora's relatives that the grave was unmarked, they were horrified.

Kathi had promised to pay for a tombstone from the royalties of her biography of Dora, but her family paid for a stone which was consecrated in 1999 on the 47th anniversary of her death.

Kathi recalled: "Seventy-five people came from around the world, 13 from Israel, including her half-sister Sara, a Holocaust survivor whose wish before she died was to see where her sister was buried."

In 2003, Kathi was able to publish Dora's biography, Kafka's Last Love.

Kathi said: "Kafka had become a caricature of his fictional, unhappy protagonists. Although there were autobiographical elements, his stories were not who he was.

"Dora described Kafka as usually cheerful, always ready for a joke. That was who Kafka really was.

"My biography rendered every previous biography incorrect. Publishers are now commissioning new biographies. Dora is officially part of Kafka literature. Her role in Kafka's life is now part of literary history.

"My story came at the right time when the new view of Kafka was being realised. Dora's point of view on Kafka was a big part of that. I had a lot of help from her."

Kathi also established the Kafka Project, which funds German universities in their search for Kafka's lost letters, thought to be in the former Soviet Union.

Last month, Kathi was at Dora's grave in East Ham Jewish Cemetery to celebrate Dora's life for the Jewish East End Celebration Society.