Peter Evans, writing in Grove, describes Britten as “the outstanding figure of the British generation that came to prominence just before World War II, at the end of which his opera Peter Grimes laid the foundation for a revival of native opera which his works continue to dominate.” Apart from those of Puccini and Richard Strauss, Britten’s operas are the most commonly performed operas, world-wide, by a composer who lived in the twentieth century, and the most commonly of all performed by a composer born in the twentieth century.

Two years after graduation from the RCM, and struggling to find performance opportunities for his music, Britten found a new outlet for his creativity in 1935 providing music for a series of films made by the General Post Office. W. H. Auden was a fellow collaborator, and the two formed a friendship. Further collaborations produced a number of song cycles, the Hymn to St Cecilia, and Britten’s first stage work, the operetta Paul Bunyan. In 1936 Britten met Peter Pears, a tenor, who was to become his life-long partner, described by Britten as “a congenial companion”, and the inspiration for many of his leading operatic roles. In 1938 Auden emigrated to California, and, in 1939, and partly to avoid conscription, Britten and Pears followed him.

A chance reading of an article by E. M. Forster about the Suffolk poet George Crabbe stirred up feelings of homesickness, however, as well as the idea for a libretto for what was to become Peter Grimes. In 1942 Britten and Pears returned to England and applied for recognition as conscientious objectors. Britten later said: "on reading that article, in a flash I realised two things: that I must write an opera, and where I belonged.” The opera asks the audience to take pity on Peter Grimes, a reclusive fisherman and social outcast, who is held responsible by the angry and disgusted residents of his village for the loss at sea of his young apprentice, and the subsequent physical abuse and death of a second apprentice. Pears was the intended Peter Grimes and sang the role at the première. Philip Brett in his essay Music and Sexuality in Britten describes the work as "a powerful allegory of homosexual oppression" on one hand, and “one of the true operatic masterpieces of the 20th century” on the other. Britten and Pears both had a strong hand in drafting the libretto, and in this process the character of Grimes became far more complex. Rather than being the clear-cut villain he is in Crabbe's version, he becomes a victim of both cruel fate and society, while retaining darker aspects in his character. The composer's own summation of the work in 1948 was simpler than Brett’s: "a subject very close to my heart – the struggle of the individual against the masses. The more vicious the society, the more vicious the individual."  Brett goes on to describe Britten as “a reluctant homosexual, a man in flight from himself who often punished others for the sin he felt he had committed himself.” According to Pears himself, “Ben’s puritanical middle-class background caused him to reject the word “gay” with its modern liberal associations.” In the two intimidating manhunts (the mob of villagers twice seeking out Grimes), which form a recurring theme in the story of the flawed and outcast fisherman, we see the terrified individual pitted against the common consensus of the masses. There can surely be no doubt about the way in which Britten identified with this emotion personally.

On returning to England, during the war years Britten and Pears gave many concerts, performing new works together. Peter Grimes was premiered in 1945 to mark the re-opening of the Sadler's Wells theatre after the war. Its emphatic success, and its subsequent and prompt acceptance at foreign opera houses, secured Britten’s place in British national musical heritage. The years following were extremely prolific. A Young Person’s Guide to the Orchestra, St Nicholas and The Spring Symphony were all just interludes in a decade of operatic activity which produced The Rape of Lucretia, Albert Herring, The Beggar’s Opera, The Little Sweep, Billy Budd, Gloriana (written for the coronation of Elizabeth II) and The Turn of the Screw.

In 1948, and in association with Eric Crozier, Britten and Pears founded the Aldeburgh Festival. The idea had initially come from Pears. Using money from his mother’s inheritance, Britten bought the Old Mill at Snape, a village a short distance from Aldeburgh, and he and Pears moved in. The Festival was an immediate success and continues to this day. New works by Britten featured in almost every Festival from 1948 until his death in 1976 and, apart from accepting an occasional commission from elsewhere (such as the 1962 War Requiem, written for the consecration of the newly rebuilt Coventry Cathedral), producing music for the Aldeburgh Festival became Britten’s prime motivation.