After the war Gardner got a job as repetiteur at the Royal Opera House. He rejected all the music he had composed (although he did not throw it away) and started again by calling his next piece his opus 1. His First Symphony was numbered opus 2. It was a mature work and made him famous. He resigned from his job at the opera house and he had time to concentrate on composing. He wrote "Cantiones Sacrae" for the Three Choirs Festival in 1952 and an opera "The Moon and Sixpence" which was performed at Sadler’s Well in 1957. 