I had no idea that I had Jewish relatives who died in the Holocaust until just a few years ago.

After my mother died in late 2013, my siblings and I began going through family papers, including my grandmother, Maud Russell’s diaries. My father, Maud’s son, had already passed away and the loss of both parents sparked a need to delve into my family history. I immersed myself in the diaries that my grandmother kept from 1937-77, captivated by the rich and active life of a very private woman who knew Matisse, Rex Whistler and Stephen Spender, among others, and was on intimate terms with Ian Fleming.

The fates of my German Jewish relations was the most significant finding of my quest to find out more about my grandmother’s life.

She was the daughter of a wealthy German Jewish stockbroker, Paul Nelke, who immigrated to Britain in the 1880s. Her mother Maria was also German, a Christian, the daughter of Carl Conrad who ran the German mint in Berlin.

My grandmother received an excellent education and went on to become one of the foremost English collectors of modern French art. She was famed for entertaining leading politicians, writers, musicians and artists at Mottisfont Abbey, my grandparents’ 2,000-acre estate in Hampshire.

Although born in England and raised in the Church of England, my grandmother was always described as “German Jewish”. This may be because my grandfather Gilbert, a cousin of the Duke of Bedford, liked challenging people’s prejudices. When telling his sisters of his engagement during the First World War he said: “Do not be alarmed when I tell you she is a German Jewess for I know you will like her. The idea of marrying a German in wartime tickles me immensely.”

As a child, I used to ask my father if my grandmother had any Jewish relations in Germany and, if so, what had happened to them in the Second World War. He always changed the subject.

As I grew older I heard stories that she’d helped her relatives flee Germany in the 1930s but they were never confirmed. Although she died in 1982 when I was 20, I never found the moment to ask her directly.

So when I began reading her diaries in April 2014, as a journalist this was one of my main areas of interest.

I was intrigued to read of her visit to Cologne after Kristallnacht in 1938 to see if her relatives needed any help. There was a “Jews Unwelcome” sign on every hotel or café she saw. “I had arrived on the day when all Jews in Germany were ordered to stay indoors between 8am and 8pm so I wondered whether my appearance might arouse comment, but it didn’t,” she wrote in her diary.

I was helped by a family tree of my German Jewish family, made in the late 1930s, found among my father’s papers.

I learnt that my great grandfather Paul had three half-sisters (his father remarried after his own mother died when he was just a few months old). Including their children and grandchildren, I counted 16 relations that I had not known existed.

My grandmother’s diaries relate her efforts to bring her relations to England, using her connections to push through visa applications.

Thanks to her help, seven relations were safely settled in England before war broke out. Her aunt Friederike Franck and cousin Lotte Franck arrived with just 10 days to spare. “Lotte said how wonderful it was to be able to go to a swimming-bath again, meaning that she was free of the restrictions that prevented Jews going to public places,” my grandmother noted.

As I read of their safe passage to England and the subsequent hearings at the Police Court and the Aliens Tribunal, I ticked off the names on the family tree. But there was an entire branch, aunt Agnes Mühsam and her descendants, where the trail ran dry.

My grandmother had obtained visas for Aunt Agnes and her son Hans Werner but they didn’t leave Germany in time and their visas were rescinded by the British government on the outbreak of war. “Tante Agnes Mühsam & her son Hans Werner disappeared from Berlin six or more months ago. Like other Jews. They are probably dead,” she bluntly recorded on 20 December 1943.

I found scraps of correspondence and notes to the diaries added after the war confirming that they hadn’t survived but with scant details. Nor did I know what had become of Hans Werner’s sisters Lieselotte Margolin and Ilse Namenyi, and Ilse’s son by her first marriage, Esra Bennathan, who were also listed on the family tree.

Esra’s birth date was recorded as 1923 and I started trying to track him down, hoping he was still alive and could tell me his family’s story.

I spent many hours in front of the computer searching for Esra. In November 2014 a German who had done research on the wider Mühsam family gave me the telephone number in the United States of someone he thought might be Esra’s wife. I rang the number and left a message on the answering machine giving my name and saying that I was looking for a relation, Esra Bennathan.

The following day his wife Judith Nowak returned my call: “Don’t worry, Emily, I can tell you that Esra is very much alive and looking forward to talking to you.” It was an unforgettable moment.

I spoke to Esra on the phone and was lucky enough to meet him on two occasions in London in January 2015 before he died the following year. At 91, he was a tiny man, impeccably dressed in a grey suit and red bow tie, large glasses over a prominent nose, his bird-like brown eyes reminding me of my grandmother.

Born in Berlin, Esra was sent by his mother Ilse to live in Palestine with his father, from whom she was divorced, in 1936 due to rising discrimination against Jews in Germany. Esra served in the British army in the war and afterwards came to England to study economics at Birmingham University. His distinguished career included posts at Cambridge and Bristol universities, the UN and the World Bank.

Esra was able to tell me of the tragic fates of Aunt Agnes, who died in Thereseinstadt camp, and Hans who survived hard labour in Neuengamme only to be accidentally bombed by the British as the Nazis evacuated the prisoners on ships just days before the end of the war. His aunt Lieselotte (my grandmother’s first cousin) had committed suicide on the French border as she was being deported into German hands by the Spanish authorities from Barcelona, where she had been working as a doctor for the Republican side in the Spanish Civil War. Only his mother Ilse had miraculously survived in the Budapest ghetto where she was living with her second husband, a Hungarian Jew.

I was deeply moved listening to Esra, hating myself for asking him questions that made him recall and relive these horrifying events. “I and my son Joel are the only Jews left in the Nelke family. The Jewishness has been washed out of them,” he told me, referring to the conversions to Christianity in other branches of the family.

I’ve often wondered why my father never talked about our Jewish relations. It wasn’t prejudice because he talked with immense pride about his mother’s Jewish ancestry.

My only explanation is that it was a taboo subject, considered too appalling to share with one’s children.

My German Jewish relatives are often in my thoughts these days as the world closes its doors on refugees, often young children, fleeing war and other horrors. I see parallels with the 1930s. I am convinced of the importance of recording the facts and keeping memory alive to try and make sure that events such as the Holocaust never occur again.

A Constant Heart: the War Diaries of Maud Russell (1938-1945), edited by Emily Russell is published by Dovecote Press.