Answer
"The Velvet Assassin" is not a play based on Corday's life because it is a novel written by Sarah-Jane Stratford, published in 2008. It tells the story of Charlotte Corday, who assassinated Marat during the French Revolution, from the perspective of her fictional maid. Plays based on Corday's life include "Charlotte Corday" (1930) by Bernard Shaw and "The Assassination of Marat" (1964) by Peter Weiss.