 The dramatist John Drinkwater saw one of Sim's productions for the school and encouraged him to become a professional actor.Through Drinkwater's influence, Sim was cast in his first professional production, "Othello" at the Savoy Theatre, London, in 1930; he understudied the three principal male roles (played by Paul Robeson, Maurice Browne and Ralph Richardson) and played the small role of the messenger.Sim followed "Othello" with productions ranging from a musical revue to a medieval costume drama by Clifford Bax, in whose "The Venetian" he made his Broadway debut in October 1931.