Marjorie Bowen

Marjorie Bowen (pseudonym of Mrs Gabrielle Margaret V[ere] Long née Campbell) was a British author who wrote historical romances, supernatural horror stories, popular history and biography (Wikipedia).

She was born in Hayling Island, Hampshire, and raised in London in straitened circumstances. Her birth name was Gabrielle Margaret Campbell—and despite the many pen names she used, and two marriages (in 1912 and 1917—she’s sometimes listed as Mrs Long) —she always regarded herself as Margaret Campbell.
Her mother strove to earn a living from writing with magazine stories, plays and novels, but only just scraped through. Young Margaret seemed to have a gift for it and though her first novel, The Viper of Milan, was rejected by many publishers, it eventually appeared in 1906 and was an immediate success.
The name Marjorie Bowen was imposed upon her to avoid confusion with her mother’s work, even though her mother wrote as Josephine Campbell.
Bowen also wrote as George R. Preedy, Joseph Shearing, Robert Paye, John Winch and, for her autobiography, Margaret Campbell.