Which was Benjamin Britten's last opera?

Edward Benjamin Britten, Baron Britten (22 November 1913 – 4 December 1976) was an English composer, conductor and pianist. He was a central figure of 20th-century British classical music, with a range of works including opera, other vocal music, orchestral and chamber pieces. His best-known works include the opera "Peter Grimes" (1945), the "War Requiem" (1962) and the orchestral showpiece "The Young Person's Guide to the Orchestra" (1945).

In September 1970 Britten asked Myfanwy Piper, who had adapted the two Henry James stories for him, to turn another prose story into a libretto. This was Thomas Mann's novella "Death in Venice", a subject he had been considering for some time. At an early stage in composition Britten was told by his doctors that a heart operation was essential if he was to live for more than two years. He was determined to finish the opera and worked urgently to complete it before going into hospital for surgery.

After the completion of the opera Britten went into the National Heart Hospital and was operated on in May 1973 to replace a failing heart valve. The replacement was successful, but he suffered a slight stroke, affecting his right hand. This brought his career as a performer to an end.