Daniel Radcliffe broke down in tears during the filming of Who Do You Think You Are? after reading his great-grandfather’s suicide note, which he may have written after suffering antisemitic prejudice at the hands of British police.

Mr Radcliffe, who played Harry Potter in the eponymous film series, learned that his ancestor, Samuel Gershon, had been financially ruined by a robbery at the family’s Hatton Garden jewellery business in 1936.

Faced with destitution and the police’s suspicions he staged the raid to claim an insurance payment, he took his life aged 42.

Mr Radcliffe said: “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.”

The insurance company eventually honoured Mr Gershon’s claim, but only after his death.

The dispute took place against a backdrop of rising antisemitism in Britain - the Battle of Cable Street took place later that year.

The programme uncovered evidence that detectives were reluctant to investigate the robbery, finding a police report that said “Jews are so frequently responsible for the bringing down of their own business premises”, the Sun reports.

Mr Radcliffe, who is descended from Russian and German immigrants, said: “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.”

Shortly afterwards the family anglicised its name, changing it from Gershon to Gresham.

The episode of Who Do You Think You Are? is due to air on July 22.