Charles Henry St. John Cooper (1869 – 1926) was a prolific English novelist of school and adventure fiction.
He wrote thousands of stories for several Amalgamated Press papers, sometimes under the pen name Mabel St.
[1] He is perhaps best known for creating, in 1908, the character Pollie Green, considered the "most popular, though not the first, in a series of irrepressible schoolgirl heroines".
[2] According to his son, he also wrote many "authorless" Sexton Blake stories for the Union Jack.
[4] Actress Gladys Cooper was his half-sister,[1] and musician Henry Russell was his maternal grandfather.