Charles Henry St. John Cooper (1869–1926) was an English novelist and story writer who became highly prolific in the realms of school and adventure fiction. Writing during the late nineteenth and early twentieth centuries, Cooper produced thousands of stories for various publications owned by Amalgamated Press. He frequently published under the female pseudonym Mabel St. John, adapting his style to suit different audiences and genres.
Among his most significant contributions to popular literature was the creation of Pollie Green in 1908. Appearing in the publication The Girls' Friend, Pollie Green became widely recognized as one of the most popular early examples of the irrepressible schoolgirl heroine archetype. In addition to his schoolgirl fiction, Cooper is believed to have penned numerous anonymous stories featuring the famous detective Sexton Blake for the story paper Union Jack, a detail later shared by his son.
Beyond his serial magazine work, Cooper also wrote standalone novels. His book Sunny Ducrow achieved notable success and was later adapted into the 1926 film Sunny Side Up. Cooper came from a family with notable artistic connections; he was the half-brother of the celebrated actress Gladys Cooper, and his maternal grandfather was the musician Henry Russell.
