On the morning of 14 August 1945 towards the end of the second world war, 16-year-old Arek Hersh and 300 other Jewish children boarded a squadron of 10 converted Stirling bombers and took off from Prague. They were organised in groups of 30 to each aeroplane, with 15 sitting on each side on the floor. Hersh remembers it vividly: “They cut us some bread,” he says. “We thought it was cake. They gave us each a piece and it was great.” About eight hours later, they landed at RAF Crosby-on-Eden, near Carlisle.

The children were the first intake of a pioneering rehabilitation scheme, in which boys and girls from labour and concentration camps in eastern Europe were transported to the Lake District to find new families and start afresh. Their journey has been dramatised by the screenwriter Simon Block and the result is a timely and moving BBC film The Windermere Children, starring Thomas Kretschmann and Romola Garai, to be shown this month, 75 years after the liberation of Auschwitz-Birkenau.

At 91, Hersh is spry with a mischievous sense of humour. For almost half a century, he spoke to no one about his Holocaust experience. Not to his three daughters, who are old enough now not only to have kids of their own but also grandchildren. Nor to Jean, his second wife, whom he married in the early 1970s. Eventually, around 1995, Hersh decided to write it all down. The words came excruciatingly slowly. “Two lines a day,” he recalls, when we meet at his comfortable home just north of Leeds. “But I wrote it, and then after that I could speak, I could talk about it.”

‘I was very, very lucky’: Arek Hersh, Holocaust survivor, photographed at his home near Leeds. Photograph: Antonio Olmos/The Observer

Before the war, Hersh – Herszlikowicz back then – lived with his parents, brother and three sisters in Sieradz, a garrison town in west Poland. His father was a bootmaker, much in demand for making officers’ footwear. When the Nazis invaded, they came first for Hersh’s father, but he escaped; they came back for his brother, but he also slipped away. That left 11-year-old Arek, who was packed off to a labour camp near Poznan to lay lines and sleepers for the Poznan-Warsaw railway, which would speed up the German attack on the Soviet Union. One of his responsibilities was to clean the room of the camp commandant, who every day would leave Hersh a hunk of bread on his desk. It wasn’t much, but Hersh believes it saved his life. “We started with 2,500 men,” he says. “Within 18 months, there were only 11 of us left alive. And I was one of them. Very, very lucky.”

“Luck” is a word that comes up again and again in Hersh’s account. When he was sent to Auschwitz in 1944, he told the SS officer that he was 17 and a locksmith. He wasn’t either of those things; he just wanted to suggest that he might be useful to the Nazis. “So that’s what I said, and they told me to go to the right side,” says Hersh. “And 180 children all went to the wrong side. And they were murdered.”

The most gruelling experience for Hersh personally, however, came in the early months of 1945, when he was evacuated first on foot, in the bitter cold, to the Buchenwald camp in Germany and finally to the concentration camp at Theresienstadt in Czechoslovakia on what he calls “the train of damnation”. “A whole month on open wagons without food,” says Hersh, shaking his head. “We ate grass. I ate the leather on my left shoe to keep going. I didn’t swallow but I chewed it.”

Your first instinct is to try to think your way into their heads. But you realise that’s impossible Simon Block, screenwriter

Hersh was in Theresienstadt, expecting any moment to be killed, when the camp was liberated by the Russian army on 8 May, 1945. He was moved on to Prague and it was here he was selected for the Committee for the Care of Children from Concentration Camps, which was set up by the British philanthropist Leonard Montefiore, a leading figure in the Anglo-Jewish Association. Montefiore persuaded the British government to accept 1,000 displaced children aged eight to 16; the Home Office agreed on condition that the funds were found by the Jewish community. In the end 650 boys and 80 girls came over.

What kind of physical and mental shape must these children have been in? How do you begin to repair the damage done to individuals, who in many cases were the only surviving members of large families? How do you try to imagine what they might be thinking? These were the questions that faced the therapists and educators at Windermere who were to help them in August 1945. It was also a quandary for the team behind the new drama.

“Your first instinct is to try to think your way into their heads,” says Simon Block. “But you realise that’s impossible. I can’t imagine what Arek, who was in four different concentration and labour camps including Auschwitz, went through. And not just for a day, but for years. You can’t recreate that trauma; all you can do is reflect how their behaviour may have manifested some of that while they were at Windermere.”

Hersh turns up the electric fire a notch and Jean walks in with a tray of tea, biscuits and cake, and instructs me with brisk hospitality to tuck in, because her husband will probably forget. On the walls are photographs of Hersh with the Queen, Prince Charles and Liza Minnelli. “Oh yes, she dedicated a song to me one time,” he says.

After landing at Crosby-on-Eden, Hersh and the other children were driven to the Calgarth estate in the village of Troutbeck Bridge. A mile from Windermere, it was a wartime housing scheme that had been used for workers from the Short Sunderland aeroplane factory, which had relocated there to evade the bombing. Dormitory accommodation was provided as well as single rooms for older boys, like Hersh. “Each one had a bed, a chest of drawers,” he says. “There was everything you needed.”

Survivors today, with the actors who play them in The Windermere Children (left to right): Chaim ‘Harry’ Olmer, Kacper Swietek, Arek Hersh, Tomasz Studzinski, Pascal Fischer, Ben Helfgott, Marek Wroblewski, Sam Laskier, Kuba Sprenger, Ike Alterman. Photograph: Helen Sloan/BBC/Wall to Wall/ZDF

The Windermere programme is not as well known as the Kindertransport initiative, which moved nearly 10,000 mostly Jewish children from Nazi-occupied territories to Britain between 1938 and 1939. At that time, some British politicians, including former prime minister Lord Baldwin, argued that it was a humanitarian duty. “I have to ask you to come to the aid of the victims, not of any catastrophe in the natural world, not of an earthquake,” he said, “but of an explosion of man’s inhumanity to man.”

Block sees clear parallels with today’s migrant crisis. “Windermere is a story of refugees and child refugees,” he says, “and I thought it was very pertinent considering what was going on at the time [in Calais] when we started working on it.”

In 1945, the immediate priorities for the children were to get clothing and find out about their families. The Red Cross supplied clothes, but they were odd shapes and sizes, so many children walked around in their underwear for a few days until donations of garments from local families started arriving.

“We started to live as normally as we could,” remembers Hersh. “Some kids brought us bicycles and they said, ‘Go on, have a ride!’ We didn’t understand what they were saying, but they gave us a bicycle. So we went on the main road, and we were cycling on the right-hand side, so they tooted the horn like mad, shouting from the cars. We didn’t know what they were shouting at us. We couldn’t speak one word of English! But we caught on quite quickly, and we went to the cinemas, sixpence per seat, and it was very nice and we made our own life and things were OK.”

News of their families took time to trickle through. For some there was hope, even something close to a miracle. There is a powerful moment in The Windermere Children when one of the children is reunited with a long-lost brother, who he has been told has probably died. That really happened. “Oh, it would be incredibly manipulative to have made that up,” says Block. “No, if you have that, you wouldn’t need to make anything up.”

For most though, including Hersh, there was only despair. He found out his mother had been gassed and thrown into a mass grave at the Chelmno extermination camp. Of his immediate family, only his older sister Mania had survived, having escaped to the Soviet Union. There is a scene in the drama where Hersh – all the children, are played by Polish actors – hears about the fate of his family and soon after breaks up with his girlfriend. “I still had so much grief,” he recalls. “I had lost my whole family and I felt I couldn’t worry about my girlfriend as well.”

At the Calgarth estate, the children received no counselling. Instead, they were encouraged to swim in the lake, play football, and given basic English lessons. “The thing about therapy obviously is that it’s only any use if somebody wants to engage with it,” says Block. “Almost the main point was to bring them together in one place where they could be with other people who’d been through what they’d been through, talk about it among themselves if they wanted to.”

That was certainly Hersh’s experience. “There were three or four boys I had been with in Auschwitz and Buchenwald,” he says. “We were always together. So I could talk to them, because they had a similar story to mine, but not to anybody else.

“We just had to suffer,” he goes on. “Terrible. I had about 30 years of nightmares. Middle of the night, I used to get a nightmare and so on.” It was only after he had completed his book, A Detail of History, in 1998, he says, that he finally began to heal. “It’s left me now. After I wrote the book actually, it left me then.”

A portrait of Arek Hersh taken when he was ‘about 18’ in Liverpool after the war. Photograph: © Arek Hersh/The Observer

The Calgarth estate programme was designed to be a temporary scheme, running for four months, after which, the younger children would be placed in the care of foster families, and the older ones would live in hostels and prepare for work. Hersh moved first to Liverpool with his friends and then Manchester. He trained as an electrician, but eventually, living in Leeds after marrying Jean, he bought and let property, mainly to students. Somewhere along the line, in the 1950s, he shortened his name from Herszlikowicz, because he was fed up with having to spell it out.

Block, who also wrote the 2015 BBC drama The Eichmann Show about the trial of Adolf Eichmann, interviewed a dozen Windermere survivors and found that most of them were “very eager to get on with life”. He continues, “They couldn’t bury what happened to them completely because it would come back in their sleep, in their subconscious, but they wanted families and all the rest of that. It was when they retired and they had more time to reflect that it all came barrelling back to them.”

Hersh is now involved in education, at schools and universities, and with the charity March of the Living, which each year organises a walk between the Auschwitz and Birkenau concentration camps. In 2009, he was awarded an MBE. “When I first went back to Auschwitz, it was awful for me,” he says. “I couldn’t get through the gate. But after three attempts I got through and since then I’ve been going there with children and young people to show them the place.”

These visits are clearly still not easy – why does he put himself through it? “Because I don’t want people to think that it just happened many moons ago, and people forgot about it,” he says. “I talk to everybody, so young people know that what actually happened to me can happen to anybody. That’s the main reason I do it.”

Block found that this idea of giving something back is a recurring theme. “The Windermere children are the most patriotic people I’ve ever come across,” he says. “They’re so grateful for the chance they got to start their lives again in the UK, and they want to express that in many ways, by being successful here and paying taxes and raising their families here.

“Hopefully viewers will think, ‘Well, it’s not impossible to bring people here and help them rather than be scared of those who might be fleeing from terrible experiences.’ We can bring them in, help them and then that’s repaid many times over.”

The Windermere Children will be broadcast on BBC Two later this month.

On 27 January, Holocaust Memorial Day 2020 will mark 75 years since the liberation of Auschwitz-Birkenau. Information on different ways to get involved in this landmark anniversary can be found here