Family researcher discovers amazing war story

When Thomas Harding went to his great-uncle's funeral he learnt a lot more about him than he was expecting. He knew he came to London as a Jewish refugee, but he didn't know he'd been sent back to Germany to track down one of the world's worst-ever war criminals.

Thomas has now written a book about his great-uncle, an unknown hero of Auschwitz.Ruth Banks went to hear his incredible story.