His theories about William Shakespeare were published in 1918 in
Sous le masque de William Shakespeare: William Stanley, Vie comte de Derby (2 vol., 1918). Lefranc argued that
William Stanley, 6th Earl of Derby was the true author of Shakespeare's works. Lefranc developed the theory after James H. Greenstreet first suggested it in the 1890s, following his discovery of a letter which stated that Derby was "busy in penning comedies for the common players". Lefranc decided that Derby's life fitted the interests and beliefs of Shakespeare the writer. Derby may have had an affair with
Mary Fitton, a candidate for the
Dark Lady of the sonnets. Lefranc considered Derby to be sympathetic to France and to Catholicism, views he also believed to be present in the plays. Derby's proficiency in French would explain Shakespeare's use of the language in
Henry V. According to Lefranc, Derby's experiences in the Court of Navarre are reflected in ''
Love's Labour's Lost.'' Lefranc also believed that the character of Falstaff was influenced by the work of Rabelais, which was not available in English translation at the time. == Principal publications ==