If he closes his eyes, Alexander Bodin Saphir can picture his grandfather, hands trembling and slightly clammy, as he pins the high-ranking Nazi’s suit.

It is Copenhagen, September 1943. In the tailor shop owned by his brother-in-law, Raphael Bodin — usually known by his nickname, Folle — is warned: “Get out while you still can. There is a round-up coming.”

Folle’s customer is most likely Werner Best, Germany’s plenipotentiary in Denmark and the deputy head of the SS. “The Butcher of Paris”, the epithet which attached to him from his time in the French capital, is no guardian angel. Nor is he motivated by a desire to help the tailor whose fine work he appreciated. Instead, Best’s warning was part of what Bodin Saphir terms a “cynical double game” to undermine Hitler’s order to make Denmark “Judenrein” so as not to upset the finely balanced relationship between its citizens and their occupiers and thus endanger the huge supply of agricultural goods to the Third Reich.

All German patrol boats were simultaneously ordered to harbour for a three-week paint job thus leaving the Øresund waterway between Denmark and Sweden largely unguarded. Although unaware of the order, this allowed the vast majority of Jews, including Folle, his wife and their baby daughter, to escape; carried in fishing boats across the narrow strait to Sweden, an event which became known as the “miracle rescue”.

Seventy-five years later, the events of that October form the backdrop to Bodin Saphir’s new play, Rosenbaum’s Rescue, which opened at London’s Park Theatre on January 7.

It is a story which always fascinated him. His grandparents never wanted to talk about the war; the memories were clearly too painful to allow questions. Bodin Saphir’s mother remembers her father mentioning in passing a high-ranking German official visiting the tailor shop. “I knew that was a very strange situation,” he says. Folle never mentioned Best’s name, but, years later, his brother-in-law, Nathan, told his daughter-in-law, Margit, the identity of the mysterious German who tipped off the family of the coming round-up. She rifled through old measurement cards at the tailor shop and was startled to find Best’s entry.

“The play is very much inspired by the ‘miracle rescue’ and very much inspired by my grandparents’ escape to Sweden,” Bodin Saphir suggests. Originally envisaged as a docudrama, he began his research at the moment when a new generation of historians were starting to question the old narrative of the “miracle rescue”. This held that Georg Duckwitz, the German naval attache in Copenhagen later honoured by Yad Vashem, altruistically leaked the date of the planned round-up to the Jewish community. Indeed, Bodin Saphir recalls one highly respected Danish historian suggesting to him that the “Danish sense of morality” may even have “rubbed off” on the Germans, causing them to turn a blind eye to the rescue of the Jews.

Bodin Saphir became “fascinated by the idea of truth and the idea of history being rewritten and the fact that facts are only facts until the next fact comes along to disprove them”.

He is keen to stress, however, that this is not an exercise in “myth debunking”. Duckwitz’ role was important and so was that of ordinary Danes and the resistance in ensuring the survival of 95 percent of Danish Jewry. “Maybe calling it a miracle is a misnomer,” Bodin Saphir suggests. “It’s more complicated and grey. ”

Set over Chanukah 2001, it features two old friends – one a Jew whose family were rescued, the other a historian – trapped by a snowstorm and talking about the events of October 1943. Their conversation takes place just weeks after the far-right Dansk Folkeparti has rocked the country’s consensual politics by running on an aggressively anti-immigrant platform and winning enough support in a general election to become a political kingmaker.

“It is harbinger of a shift to the right in global politics,” believes Bodin Saphir. “I think it is a really interesting moment to set a play, to have a discussion about Danish liberal progressivism and the coming political storm we now find ourselves in.”

“What does that mean for a people who rose up as one to save their Jewish brothers and sisters and rose up not because they were Jews but because they were Danes?” he asks. “I don’t know if that would happen today given the current political climate.”

Rosenbaum’s Rescue is at the Park Theatre, London N4 until February 9