The letter is now on display at the United States Holocaust Memorial, her son Frank Grunwald wrote an article for Sky News about the note for today’s Holocaust Memorial Day. Mr Grunwald said it took him years to decide to read his mother’s heartbreaking letter, which she had written to his father before she died. He said: “And when I did eventually read it, I found it really disturbing because I was immediately in her situation.

“But I also amazed about how positive and how calm she was in the letter.

“My mother’s brave words lacked any anger or hatred towards the Nazis and instead was just so positive.”

The letter read: “You, my only one, dearest, in isolation we are waiting for darkness.

“We considered the possibility of hiding but decided not to do it since we felt it would be hopeless.

“The famous trucks are already here and we are waiting for it to begin. I am completely calm.

“You – my only and dearest one, do not blame yourself for what happened, it was our destiny.

“We did what we could.

“Stay healthy and remember my words that time will heal – if not completely then at least partially.

SEE MORE: We survived Auschwitz and thought we were safe. 

“A transport of around 5,000 inmates had arrived at the camp in September before us and we were part of the second batch of 5,000.

“We had no idea why we were there.

“We were kept in a Czech family camp which was a ploy by the Nazis to show the International Red Cross that Czech Jews were being well looked after.

“At the time, we had no idea why the family camp was even established because most of the time, when children arrived at the Auschwitz railway station, they were almost immediately killed in the gas chambers.”

More than one million people were killed in the Auschwitz concentration camp, which was liberated by the then Soviet Union on January 27, 1945.