The Ninth Legion of the Roman army was last recorded in York in around AD 107. After that it simply vanished from history. To this day no-one knows what caused the destruction of this elite army unit, although many theories have been put forward. As we continue our series on history’s most puzzling events, Miles Russell explores the various possibilities and explains what he think is the most likely reason for the legion’s disappearance. See acast.com/privacy for privacy and opt-out information.