When François Matarasso visited Thessaloniki, he immediately felt at home. In some way’s that’s unsurprising — his father Robert’s family had lived in the Greek city, then known as Salonica, for generations. His grandfather Isaac was a respected doctor there, still remembered today for his compassion. And yet this was the site of the Matarassos’ worst times, the place from whence François’s great-grandfather and up to 50,000 other Jews were deported to Nazi death camps.

Many were sent to Auschwitz; only an estimated 2,000 returned. A community dating from the arrival of those fleeing the Spanish Inquisition would never recover.

Robert and Isaac were the “lucky” ones. Escaping torture and imprisonment, they joined the resistance and when the few survivors trickled back, they were there to help them, with Isaac providing medical care and his teenage son supporting him.

Their survival against the odds is astonishing, but more so is that Isaac had the prescience to take notes, building a meticulous account of the community’s fate. In And Yet Not All Died, completed in January 1946 and published two years later, he writes: “Dear Jews of Salonica, I have used my weak voice to bring many of the stages of your calvary to public knowledge.”

He recorded in painstaking detail statistics, dates of deportations and numbers taken, the restrictions placed on Jews, medical records (including of survivors) and more.

He included first-person descriptions of Auschwitz from the first to return. Leon Batis, who arrived back in May 1945, tells Isaac “I’ve passed through different countries, and more or less everywhere they took me for a madman”. Isaac logged every detail, from the transportation to the selections, the brutality of the guards and the horrors that unfolded.

His account is now being released in English for the first time, as part of a book, Talking Until Nightfall, that is part history, part memoir (as written by Robert before his death in 1982) and part analysis.

Publication is thanks to Robert’s British widow Pauline, a professional translator, and their son François, now 61 and a community artist who divides his time between France and Nottingham.. “I’m very conscious that there is a point at which the last people who knew this first hand are dying,” says François.

Publishing “felt like the discharging of a responsibility, because it ceases to be simply stuff we know and becomes another little stream that joins the river of history.”

Isaac comes across as extraordinary; a cosmopolitan doctor with a strong sense of duty. François has encountered people who were treated by him as children. “The memory of him remains very warm and evocative in the Jewish community in Greece and that is very moving.”

“In my mind he is still really alive and very present, because he was that kind of person,” recalls Pauline, now 91 and living in Oxford. Even at the end of his life, “he was so determined to go on living”.

The Salonica Isaac was born into in the tail end of the Ottoman Empire was culturally diverse “and didn’t have a problem being so”, explains François. Jews were one of the largest groups but the population was mixed, with Greeks, Turkish Muslims, and smaller communities of Bulgarians, Spanish, Italians and, Germans.

“It’s really important not to idealise because of course there were tensions, but I don’t have a sense that any of those groups questioned the legitimacy of the others,” says François. Boosted by the Alliance Israélite Universelle, which set up Jewish schools across the Ottoman Empire, Salonica was a modern community, with a thriving Jewish professional class alongside a big working class of dockers, porters and other trades.

Isaac studied in France, there meeting his Catholic bride. Robert, accordingly, was not brought up to focus on his Jewish lineage (although Pauline emphasises he was close to his relatives and still grew up within the community). Some of the most affecting passages are Robert’s descriptions of a friend rejecting him after he was forced to wear a yellow star. “It was a shock to discover [being Jewish] could be held against him, that this was a bad thing to be. I don’t think that had ever occurred to him,” says Pauline.

She herself is not Jewish, although she had early exposure to the experiences of Jews under the Nazis, thanks to her mother hiring a German Jewish refugee as a governess just before the war. “My mother felt very strongly about this, and looked for her in particular, so I knew something about Jewish communities and their persecution by the time I was ten, which in England at that time was not very common.”

François, for his part, refers to himself as Mischling, co-opting the derogatory Nazi term for those of mixed blood.

“My whole sense of identity has been of not belonging and I neither feel Jewish nor not Jewish. Clearly I wasn’t brought up in that way but I was brought up with an enormous body of tradition and sense of love for a group of people who were my relatives.”

The Matarassos left Salonica after the war, first for Athens and then France. François has visited multiple times. “I have never felt so welcomed or accepted anywhere as by Jewish communities in Salonica and Athens. People knew my grandfather, so I don’t have to explain myself, it’s the only place where I have that sense of belonging.”

The family had lived there for generations; Aaron, Isaac’s father, was a currency trader and community stalwart, known for distributing sweets to local children. His life was marked by tragedy; Isaac’s mother and sisters were killed on a return visit from France in 1918, when their ship was torpedoed. When the Nazis came in 1941, Aaron was living in the old people’s home; he was sent to the gas chambers at Auschwitz.

Tragically, his son had been about to take him away. “They went in the afternoon and the home had been emptied by troops in the morning,” says François. The loss played heavily, but it was one of many. “There were so many people, so many friends and relatives who died. Collectively there was an entire world that was destroyed.”

By the time the Nazis occupied Salonica, the war had been raging for 18 months; yet few had a sense of what was to come. “There was not the history of antisemitism that had characterised many Jewish people’s lives in eastern Europe,” points out François. It was less than a quarter of a century since Salonica had gone from being Ottoman to Greek; the population had endured spurts of democracy and dictatorship, plus conflicts like the Italian-Greek war.

“It had seen the expulsion of Turkish Muslims and the arrival of several hundred thousand Christian Greeks,” says François. “Instability was part of what happened and people largely thought it was something you got through. It was a very different context.”

Pauline suggests Isaac’s decision to record events was instinctive; simply what scientists did. But the original draft of And Yet Not All Died contains warnings for future generations that “one day new ‘supermen’ may single out other races as ‘inferior’ and decree their eradication’.” François suggests perhaps he understood, in some way, that gathering evidence mattered.

“If you reread the testimony of the first people who came back, they all say the same thing, which is what we’ve seen is not believable, people think we’re mad,” he says. “[The Holocaust] still seems incredible today, but at least now we have seen the evidence. I think in those first few years it was inconceivable. I think he understood without necessarily considering it from a political perspective that there would be people who would want to gain political advantage from denying it.”

Beyond the history of what the Nazis did, Talking Until Nightfall tells another story; of a world now lost forever.

“I’m conscious of romanticising Salonica because I only knew it through my father’s pre-war stories, but it has always remained a very important symbol of the kind of Europe that Europeans spent two world wars destroying,” says François. “For me the European 20th century is an enormous lesson in what happens if you fail to accept others and their right to be amongst us.”

Talking Until Nightfall: Remembering Jewish Salonica, 1941–44, is published by Bloomsbury