One of the biggest mysteries of the Second World War is: who betrayed Anne Frank and her family?

Anne Frank is perhaps the most prominent holocaust victim in the world. Her diaries shed light on what it was like to hide from the Nazis in their tiny space behind a bookcase in the building where Anne 's father, Otto, was working in Amsterdam.

Reconstruction of the bookcase that covered the entrance to the Secret Annex, in the Anne Frank House in Amsterdam

Her family hid from 1942 to 1944 until they were captured and given over to the Gestapo, the Nazi secret police. Only Anne Frank 's father, Otto, survived the concentration camps they had been sent to. A century of people lost in the fires of genocide and ignorance.

A model of the building where Anne Frank stayed, including the Secret Annex.

Although what happened to Anne and her family is well documented, we don't know who betrayed the Franks and why.

Historians were hopelessly debating back and forth about the Frank family. A number of people are suspected of betraying the inhabitants of the secret room, but none of them has been definitively identified as the guilty.

Otto, the only survivor of the Frank clan, assumed that his betrayer was a warehouse worker named Willem van Maaren, who had worked for him before the war. Throughout the war, Willem van Maaren believed that the Franks were living inside the Secret Annex-which was very surprising since he was the only one to warn people about the Franks' hiding location.

After the war, Willem was charged for betraying Anne and her family. Yet, luckily, there was not enough evidence for him that he had snitted the Jews in the warehouse, and that he had been set free along with other suspects.

Another theory is that there was no betrayer at all. The special police who found the fugitives typically investigated cases involving money; they certainly did not specialized in weeding out hidden Jews. As the theory goes: the police were investigating allegations of unauthorised jobs and bogus food ration cards when they inadvertently approached the Frank family.

In the end, with all the controversies and discussions going on over who betrayed Anne Frank for the last 7 decades after her death, there's probably no chance we'll ever learn who wanted to snitch Anne 's family, whether someone did it first.

But who knows that. Maybe someone will discover a hidden document that shows how the eight Jews living behind the bookshelf were caught. Since then, however, all efforts to discover the identity of the betrayer have been fruitless.