A collection of letters from Heinrich Himmler — a leading architect of the Holocaust — has turned up in Israel.

The banality of many of the letters makes them horrific. For instance, amid casual observations to his wife Himmler incidentally mentions an upcoming visit to Auschwitz, signing off: “Your Heini”.

The sensational find is the theme of a new film by Israeli director Vanessa Lapa, whose father now owns the collection. The film, The Decent One, will premiere at the Berlin International Film Festival. The letters have been confirmed as authentic by the German Federal Archive.

Among the roles Himmler fulfilled for his “Führer” was to organise the Einsatzgruppen, or mass-shooting squads, and to oversee the operation of concentration camps.

According to Die Welt, the collection contains hundreds of letters, notes and previously unknown photos, as well as recipe books. The journey of these papers reportedly began when US soldiers took them from the Himmler home in May 1945. Yedioth Achronoth has suggested that Israeli collector Chaim Rosenthal purchased the material at a Belgian flea market in the 1970s. It was then reportedly kept in a Tel Aviv apartment for decades until the Lapa family bought it.

Himmler’s great-niece, Katrin Himmler, told Die Welt that Heinrich Himmler “was not a split personality. The letters reveal the same hardness and coldness applied to raising his children, as he showed elsewhere.” Katrin Himmler lives in Israel with her husband, a child of Holocaust survivors.