From Benford's Gilbert and Sullivan Lexicon:
The theatrical entrepreneur Richard D’Oyly Carte was convinced that English audiences would pay to attend respectable, well-written and well-produced musical entertainments. He was also convinced that he knew who among his contemporaries were most likely to write the works he envisaged. Although Thespis had been a modest success, Carte was sure the team could do even better. He knew that Gilbert was the nation’s best-known wit and dramatist, and that Sullivan was England’s preeminent composer. Given the right encouragement, surely they could work together to produce first-class musical theater. Carte succeeded in effecting this collaboration when he commissioned them to write Trial by Jury. Gilbert had at hand a libretto based on one of his earlier ballads (in the form of a brief operatic sketch) and Sullivan quickly set it to music. The mini-opera was intended to fill out a program built around Offenbach’s La Périchole, and was first performed at the Royalty Theatre on March 25, 1875. Gilbert labeled it “A novel and entirely original dramatic cantata, in one act.” Trial soon became more of an attraction than La Périchole, and Carte knew he had been right in assessing the worth of Gilbert and Sullivan as a team. This view was emphasized by a reviewer for the Times, who wrote that Sullivan’s score fitted Gilbert’s words as though words and music had proceeded from the same brain. This turned out to be an astute observation that was frequently applied to all the pair’s joint operas (178, 275).
Trial by Jury ran for 131 consecutive performances, and still delights audiences everywhere. The plot is simplicity itself. The scene is a courtroom where a jilted bride is suing her former fiancé. After considerable argument –– much of it carried off in mock Italian/Handelian operatic style –– the judge determines to make everyone happy by marrying the plaintiff himself. Being himself a lawyer, Gilbert had no difficulty in poking this sort of fun at the British legal system. There are no spoken lines in the opera and the music sparkles from beginning to end.