From Benford's Gilbert and Sullivan Lexicon:
All friction between Gilbert and Sullivan was dissolved -- at least for a time -- when Gilbert hit on the idea of setting the next opera in Japan, turning his back on topsy-turvydom and the magic lozenge -- also at least for a time. Although the setting was Japanese, the butt of Gilbert's wit was very much English, albeit kimono-clad. Everything about The Mikado fell perfectly into place. The story line is clever, the characters are nicely drawn, the lines are witty, and the music is of enduring beauty and perfectly suited to the words.
The Mikado opened at the Savoy on March 14, 1885, and ran for a record-breaking 672 performances. It remains the most popular of all the Savoy operas and may well claim to be the most-often-performed theatrical work in world history (182).