Helen Ruth Castor FRSL is a British historian of the medieval period and a BBC broadcaster.Castor was Director of History at Sidney Sussex College for eight years before focusing on writing and media.In 2005, she published her first book, "Blood and Roses", about the Pason family, who lived in the 15th Century and whose letters are the earliest surviving collection of private correspondence in the English language. In 2010, she published "She-Wolves".Castor has appeared multiple times on BBC Radio. She was the presenter of Radio 4's "Making History" and "She-Wolves".