Were top Nazi leaders mad? Were they evil? Were they like religious fundamentalists, committed to a deranged ideology? Or were they just amoral narcissists grasping for power in the wrong place at the wrong time?

Jack el-Hai wrote the book which became the movie "Nuremberg", in which Russell Crowe plays Hermann Göring. In Nuremberg jail, awaiting trial, 22 senior Nazis were interviewed by a young U.S. Army psychiatrist.

Psychiatrist Dr Douglas Kelly was only supposed to assess the Nazis’ mental fitness to stand trial. But he became obsessed with identifying a “Nazi personality”. He spent months with Goering, the man who was to succeed Hitler, hunting for traits or disorders that could identify who might commit such atrocities in the future. His private notes were kept secret by Kelly’s family until they released them to Jack.

He joined Josh to share what he learned, and what we all should understand about evil.