This year sees the 500th anniversary of the moment when Martin Luther sparked the Reformation by - tradition has it - nailing his 95 theses to a church door in Wittenberg. Ernie Rea and guests discuss what led Luther to take this step, how his thought and personality affected the course of the Reformation and whether - were he to walk into the 21st century - he might actually find himself to be a good Catholic.

Producer: Rosie Dawson.