Daniel Radcliffe goes on an emotional journey in Who Do You Think You Are? after he discovers his great-grandfather's suicide note.
The Harry Potter, 29, star breaks down in tears in the new series as he reads the letter penned by his relative Samuel Gershon.
Daniel's great grandfather had been left destitute and shamed after a robbery at the family's Hatton Garden jewellery business in 1936.
But when he reported it to police they accused the Jewish businessman of faking the crime so he could claim the insurance.
Poor and unable to provide for his family he went on to take his own life.
In the episode, which is set to air on BBC One on Monday July 22, Daniel says: "Everything he had worked for and that his father had worked for, has sort of been destroyed.
"You want to just reach into the past and just go ‘whatever you’re going through, you have so much to offer the people who are around you still . . . you have so much to give to them.
“And, they still would all have loved you’.”
Daniel discovers that despite no proof of the robbery, the insurance company did eventually pay out on the claim but only after his death.
The actor was shocked to learn that there was strong evidence the British police detectives were anti-semitic and appeared not to want to investigate the crime properly.
According to the Sun the police report said: “Jews are so frequently responsible for the bringing down of their own business premises.”
Daniel says: "There’s a lot to dig into in that one sentence. It’s very jarring to see being a Jew to be taken as a piece of evidence in itself."
In the episode Daniel also learns more about the women in his family as well as uncovering a photo of his great, great grandfather Louis, who he looks strikingly similar to.
Who Do You Think You Are? airs on Monday July 22 on BBC One at 9pm
