Katie Emanuel was born to a prominent English-Sephardic Jewish family. Her father Emanuel Emanuel, was Justice of the Peace for Southsea. Katie was educated privately at home by governesses. In 1870, she married Sir Philip Magnus, a member of Parliament and educator, with whom she had three children. Lady Magnus contributed a large number of prose and poetry works to the Westminster Gazette, as well as articles for the London Spectator, the National Review, and other popular magazines and periodicals. She served on various committees for the Berkeley Street Synagogue, and was active on behalf of several Jewish charities. She also wrote on Jewish topics, including About the Jews Since Bible Times (1881), Jewish Portraits, and Outlines of Jewish History, which ran to three editions and was republished with additional chapters on America by the Jewish Publication Society of America in 1900. A collection of her works and papers was published under the title Salvage (1899). Her other historical works included First Makers of England (1901).