It was the morning of 16 December 2021, a week before Christmas. Across from me sat Brigitte, the daughter of Rudolf Höss, the commandant of Auschwitz. I was here to ask what life was like next to the camp.

Brigitte was 88 years old. With pale lips, thin arms and wisps of white hair, she was frailer than she had been the last time I saw her. Her voice was weaker too, her speech more languid and halting. But she was still able to think clearly and her eyes still sparkled with life.

We were sitting in Brigitte’s curtains-drawn house in the suburbs of Washington DC. The neighbourhood was full of senators, lobbyists and lawyers. The streets were wide and lined with trees that had long lost their leaves.

Next to me stood a scraggy Christmas tree. From its branches hung homemade ornaments that decades before Brigitte had brought from Germany. “Mutti made many of those,” she told me with a fond smile. Mutti was Hedwig Höss, the wife of the commandant of Auschwitz.

I had first interviewed Brigitte in 2013. Up till then, she had said little to her children about Auschwitz. She had never before spoken to a journalist. It had taken me three years to persuade her to talk with me.

In all, I spoke with Brigitte for more than 20 hours. This became the basis for an article I wrote for the Washington Post which was syndicated around the world. It was the first time that one of Rudolf Höss’s children had chosen to speak publicly, the first time that one of them had opened up about life in the villa next to the camp.

During these interviews, Brigitte had provided the basic facts: in 1940, she had been seven years old when she arrived at the camp with her family. She had remained at the villa till 1944 when they moved to Berlin for the final months of the war.

In April 1945, just before the Soviet army took Berlin, her father had gone on the run. He took on the identity of a seaman and worked at a farm near Flensburg in northern Germany. Brigitte, her mother and siblings hid in a nearby sugar factory.

A year later, a captain from the British army was given the job of searching for Brigitte’s father. This captain happened to be my great-uncle, Hanns Alexander, who was a German Jew from Berlin. He found Brigitte and the others in the sugar factory and demanded to know where her father was hiding. Brigitte told me that he shouted so hard at her that for the rest of her life she had headaches. With information provided by Hedwig, he tracked down Rudolf Höss and arrested him. I later wrote a book about this story, Hanns and Rudolf.

Brigitte left Germany in the 1950s and started a new life in Spain. For three years, she was a model for Balenciaga in Madrid, where she met her Irish-American husband, an engineer. They moved to Washington in the 1970s and Brigitte worked in a fashion boutique for 35 years.

In the years since carrying out these interviews, I came to realise that there were gaps in the history. Episodes that needed completing. Questions that needed to be answered. I wanted to get Brigitte on the record one last time before it was too late. For the sake of history. It would be one final interview.

So it was that eight years later, in December 2021, I was once again sitting in Brigitte’s living room in the gloomy and cluttered house outside Washington DC. “What was your first memory?” I started by asking. “Auschwitz,” she said. “I don’t remember anything before that.”

And her siblings, what were they like? “I was closest to my younger brother, Hans Jürgen,” she said. “I had most fun with him. I went horseback riding with my sister.” Brigitte slept in the villa with her sister Heidetraud. Her two brothers Klaus and Hans Jürgen shared a bedroom while baby Annegret slept in a little basket in a room with a nanny who looked after her. “I remember we had fun,” she said, “We had a little swimming pool in the backyard. And my mother had a beautiful garden house with flowers. She loved flowers. I inherited that, I love flowers too.” They also had pets. Two tortoises called Jumbo and Dilla and two big dalmatians.

But she was always aware of danger. When there was an air-raid warning they had to dash to the basement. “We had a little suitcase next to our bed with clothes in it,” she recalled. “We picked it up and went downstairs when my mom said: ‘Let’s go downstairs.’”

Her mother and father were very close, Brigitte told me. “They loved each other.” At the weekends, her father didn’t have to go to what she called “work”. He could spend time with his family.

“He was a wonderful dad,” she said. “On Sundays he smoked a cigar through the whole house. We had breakfast, lunch or dinner, like a nice family.” She then added: “We didn’t even know what his work was really.”

One of her favourite times of the year was Christmas. Her parents would hang ornaments on the tree and when they were finished her father would ring a bell. Brigitte made a ting-a-ling sound when she recounted this story.

“Dad then opened the door. And there was a tree with all the lights on, real white candles. And so you could look at it. But first we had to eat Christmas Eve dinner. And then after this we could get under the tree. Always there were real cookies. And we could get some down. And eat some. Not all, just a couple.”

Brigitte said she knew that the people who worked in the villa and garden were prisoners in the camp. “They were always very happy,” she said. “They called my mother, the Angel of Auschwitz.” Seeing my surprise, Brigitte said: “My mom was just a nice person. Period.”

In the 1970s, Hedwig visited Brigitte in Washington but they rarely discussed Auschwitz. “It was too painful,” she said. “I’m sure my mom knew what was going on [in the camp]. She was very sad about it. But she couldn’t help. She just tried to be nice with the children and with my father.”

Before he was hanged in Auschwitz, in April 1947, Rudolf Höss wrote his final words to Brigitte and her sister Heidetraud. I read this to Brigitte:

“You are yet too young to learn the extent of the hard fate dished out to us. But you especially, my dear good girls, are specially obligated to stand at your poor unfortunate mother’s side and with love assist her in every way you can. Surround her with all your childlike love from your heart and show her how much you love her.”

“That just sounds like my dad,” she said when I finished. “I love it.”

So what was her father like? I asked. “He was a wonderful, absolute wonderful person,” she said. “I couldn’t have wished for a better father.”

Was he affectionate, I asked?

“Oh, yes,” she replied. “He was always hugging. At night, he would give us a kiss and tell us: ‘Schlaf schön Nacht meine Kinder’ [Sleep well my children].”

Brigitte paused. “Later, we found out what’s going on. I don’t really like to talk about it because I didn’t like this idea what they did. But I know it was not my dad’s fault.” She paused again, before adding: “I don’t think he knew what he got into when he started. Because he was very unhappy many times. And when I talked with my mom after all this happened, you know, she told me he was a very unhappy man.”

I pushed her on this. How could her father be an “absolute wonderful person” if he was responsible for the murder of over a million women, men and children?

“Well …,” she stammered.

“That’s a fact. Isn’t it?” I said.

“Yeah,” she conceded. “But I don’t think … I mean I don’t see it like this.”

“But it’s true. You do agree it’s true? You know, it’s true?” I pushed.

“Well, it happened,” she said weakly.

“It happened at Auschwitz?” I said to be clear.

“Yes,” she said, her voice barely audible.

“And your father was the commandant?” I continued.

“Yes,” she said again.

“So he was responsible?”

“Like I said, things happen sometimes.” She then waited a moment, and added: “Maybe I don’t want to know certain things.”

“But it’s true,” I pressed. “You know that he was responsible. You do know that?”

“I still don’t believe it,” she still resisted, “because there were people on top of him, who made him do this.”

“But he still did it.”

“Well, yes, I guess,” she at last conceded, “I have to say yes.”

And with that the interview was over. I packed up my recording equipment, put away my notes and said goodbye.

Less than two years later, in October 2023, Brigitte died. The only one of her siblings still alive is Annegret, but she was just a baby when they lived at the camp. And so with Brigitte’s death we have lost the last person to remember what life was like for the commandant’s family who lived in the villa in Auschwitz.

On 10 March 2024, The Zone of Interest won two Oscars for best international feature film and best sound. This film tells the story of what life was like for the Höss family in the villa next to Auschwitz. It was released after Brigitte died.

I am therefore glad that I was able to record her testimony on the record for the sake of history, for the sake of anyone who wants to understand how human beings are capable of carrying out such an atrocity, for anyone who wants to stop such things from happening again.

• Thomas Harding is the author of Hanns and Rudolf (Windmill, £12.99)

You can follow him on X: @thomasharding