William Sydney Penley was an English actor, singer and comedian who had an early success in the small role of the Foreman in Gilbert and Sullivan's Trial by Jury. He later achieved wider fame as producer and star of the prodigiously successful Brandon Thomas farce, Charley's Aunt and as the Rev Robert Spalding in several productions of Charles Hawtrey's farce The Private Secretary.

Trial by Jury is a comic opera in one act, with music by Arthur Sullivan and libretto by W. S. Gilbert. It was first produced on 25 March 1875, at London's Royalty Theatre, where it initially ran for 131 performances and was considered a hit, receiving critical praise and outrunning its popular companion piece, Jacques Offenbach's La Périchole. The story concerns a "breach of promise of marriage" lawsuit in which the judge and legal system are the objects of lighthearted satire. Gilbert based the libretto of Trial by Jury on an operetta parody that he had written in 1868.