Helen Castor is a medieval historian and a Bye-Fellow of Sidney Sussex College, Cambridge. Her first book, Blood & Roses, a biography of the fifteenth-century Paston family, was longlisted for the Samuel Johnson Prize in 2005 and won the English Association's Beatrice White Prize in 2006.

Her second book, She-Wolves: The Women Who Ruled England Before Elizabeth, was made into a BBC2 TV series, and selected as one of the books of the year for 2010 in the Guardian, Times, Sunday Times, Independent, Financial Times and BBC History Magazine.

Her most recent book, Joan of Arc, was dubbed 'a triumph of history' (Guardian).