It started just before my 70th birthday. It was 2021 and I had spent the year researching stories about one of the Nazi concentration camps, Belsen, wondering if it would provide the basis for a new book. Discussing my findings with my son, he said to me, ‘Why do you always write about other people? What do you know about your own father’s war story?’

The gauntlet was down. I had no excuse since I live very close to the National Archives at Kew, where I had often researched other stories and where I knew my father’s army file would be held.

A week later, as we celebrated my birthday, my son gave me a gift; he had done the initial digging and presented me with my father’s file references. This meant I could request the information in advance without having to queue at the information desk. (The archives at Kew are busy; always full of amateur genealogists wanting to know more about their ancestors.)

My father joined the army in 1938 and left at the end of 1945. He died almost three decades ago and in his final years I had tried coaxing out his memories, documenting them on a tape recorder.

I never got much further than the horrific battle for Caen, in Northwest France, when he rescued a stray spaniel, put the dog in his tank and brought her back to England at the end of the war. I knew we were skirting the real war.

When we got to the subject of Belsen, his voice dwindled. He was not present at the liberation in April 1945, he told me, and the subject was dropped.

But I knew that he and his platoon had been there the month after. By then my father had been promoted to quartermaster general so was in charge of writing the regimental diary. Now, in the archives at Kew, I could read his real-time typed accounts of the enormous problems faced by thousands of displaced persons: where to send them, how to feed them (not too much!) and how to keep order. At the bottom of each page, I saw his unmistakable signature: Eric Rubinstein. I felt a shiver at the thought of all that he had witnessed, and at the same time guilt. How could I call myself a historian yet have failed to interview someone who was present as history was being made?

I continued reading his notes. In a summary of the War Diary for 24 May 1945 there was written: ‘C Squadron 7R Tanks burning Belsen camp with Crocodiles.’ He was organising the powerful Churchill Crocodile flame-thrower tanks to destroy the lice-ridden huts.

I knew that on 24 May 1945, the surviving Jewish members of the women’s orchestra of Auschwitz, who had been sent to Belsen by their Nazi captors some months earlier, had given a Red Cross concert. It was a bittersweet moment. My father must have attended the concert – how could he not have? He loved music and where else was there to go? But now I could not ask him.

I realised I had to write my book about the women’s orchestra of Auschwitz.

I never expected to establish a firmer connection between my father and the orchestra, but I felt magnetised by the subject of female courage in wartime and was convinced my father must have crossed paths with some of the players.

Camp orchestras were not unusual. There were 15 in Auschwitz alone, entirely comprised of prisoners. The orchestras were used as marching bands, to give the impression of a military, rather than an extermination, camp. They were also used to make inmates going to and from work keep time in rows of five; that way, it was easier for the Nazis to count them. The other prisoners, unsurprisingly, saw this perversion of music as an additional form of torture.

But there was only one all-female orchestra in any of the Nazi prisons, camps or ghettos. One of its Nazi organisers was Maria Mandl, SS chief guard of the women’s camp at Auschwitz, who wanted to impress her Nazi lover with how cultured she was. In August 1943, Mandl discovered Alma Rosé, a formidable Austrian violinist and the niece of composer Gustav Mahler, who was imprisoned in Auschwitz. Quickly, Mandl put Rosé in charge of what had been until then a small and floundering group of musicians, who were just about able to play a few Polish folk songs from memory.

Rosé doubled the size of the orchestra to around 50, recruiting music copyists and singers. The group was not sent out to work during the day but instead practised for hours in between the marching sessions. In return for playing well, members had their own block, an individual bed, underwear and were allowed to grow their hair. Hardly privileges but enough to make them resented by some of the other women prisoners. The real privilege of playing in the orchestra was that they were not selected to be killed in the gas chambers, which, for Jewish women, was the likely outcome of being in Auschwitz. (Although Rosé would tell her girls that if they did not play well, they too would ‘go to the gas’.)

Rosé died in April 1944, aged 37, from possibly intentional food poisoning. In the eight and a half months she spent in charge of the orchestra, she had managed to save the lives of around 50 women and girls.

When I started my research, all the information said that there was one surviving member of the women’s orchestra, the cellist Anita Lasker-Wallfisch, who moved to London in 1946. She married pianist Peter Wallfisch in 1952, had a family and became a founder member of the English Chamber Orchestra. I was warned by those who knew her that she did not like journalists who had not done their homework. I read her memoir thoroughly and tried to learn as much about her as I could.

Our first meeting, at the North London home where she had brought up her two children, was brief. Then 96, she was unsurprisingly fed up with giving the same account again and again. Things changed when I told her that two of my children, now adults, had learnt the cello from a young age. Suddenly she became animated, telling me of her own grandchildren, now also musicians. She said, ‘Whatever else the Nazis thought they could kill, you cannot kill music.’

She agreed to see me again. In the end, we established a warm relationship and I met her four times, listening to whatever she said with rapt attention, even if the answer to some of my questions was simply that she could not recall such details. She remembered the overall nightmare all too clearly, including the day Josef Mengele, the Auschwitz doctor known as ‘the angel of death’, wandered into the music block and demanded she play Schumann’s Träumerei.

‘I played it as fast as I could so he would leave.’

Here was a living witness to hell; by playing the cello as a 17-year-old teenager, Lasker-Wallfisch had survived. She put it down to luck, possibly true since she is almost never without a cigarette in hand or mouth, a habit she began in Auschwitz.

At the end of 2022 I discovered something even Lasker-Wallfisch did not know. There was another orchestra member still alive: her friend Hilde Grünbaum Zimche was nearly 100 and living in Israel. It had been announced in The Bookseller that I was embarking on this book, and the granddaughter of another member of the women’s orchestra of Auschwitz got in touch to tell me about her.

I flew to Tel Aviv and interviewed Grünbaum Zimche at the kibbutz where she had lived since her marriage in 1947. I took the photograph of my father in his uniform to show her, hoping there might be a flicker of recognition – but no. However, she politely said she remembered the uniform, and what a relief it was to find men in uniform who were helpful, as the British had been.

An abscess in Grünbaum Zimche’s neck meant she became unable to hold a violin. ‘Then I was frightened,’ she said. But Rosé allowed her to stay, working as a copyist.

On Sundays, the orchestra gave the Nazi officers a concert; soothing music apparently made several of them feel better after a brutal killing spree. Grünbaum Zimche recalled, ‘I remember Anita used to say to me, “Who can understand these people? One minute they want Schumann’s Träumerei, and the next they are putting people in the fire.”’

As soon as I returned to London, I phoned Lasker-Wallfisch to give her a full account of my meeting. Grünbaum Zimche had moved to a different part of the kibbutz so the women had lost touch. That year, on the anniversary of Belsen’s liberation, the two women spoke on the phone. They spoke again for Grünbaum Zimche’s 100th birthday in August 2023. Six months later she died.

It was a privilege to have met these two extraordinary women and, through them, catch a glimpse of their comrades. As I look at the photograph of my father in his army uniform, back on the shelf by my desk, I realise I still have not exactly written about him, but I have grown markedly closer to him, by entering into his world before I was born.