- Allan Corduner - Arthur Sullivan
- Timothy Spall - Richard Temple
- Martin Savage - George Grossmith Sr.
- Shirley Henderson - Leonora Braham
- Kevin McKidd - Durward Lely
- Vincent Franklin - Rutland Barrington
- Dorothy Atkinson - Jessie Bond
- Cathy Sara - Sybil Grey
- Louise Gold - Rosina Brandram
- Eleanor David - Fanny Ronalds
- Matthew Mills - Walter Simmonds
- Jim Broadbent - W.S. Gilbert
- Lesley Manville - Lucy "Kitty" Gilbert
- Ron Cook - Richard D'Oyly Carte
- Wendy Nottingham - Helen Lenoir
- Sam Kelly - Richard Barker
- Andy Serkis - John D'Auban
On the opening night of Princess Ida at the Savoy Theatre in January 1884, composer Sir Arthur Sullivan, who is ill from kidney disease, is barely able to make it to the theatre to conduct. He goes on a holiday to Continental Europe hoping that the rest will improve his health. While he is away, ticket sales and audiences at the Savoy Theatre wilt in the hot summer weather. Producer Richard D'Oyly Carte has called on Sullivan and the playwright W. S. Gilbert to create a new piece for the Savoy, but it is not ready when Ida closes. Until a new piece can be prepared, Carte revives an earlier Gilbert and Sullivan work, The Sorcerer.
Gilbert's idea for their next opera features a transformative magic potion, which Sullivan feels is too similar to the magic lozenge and other magic talismans used in previous operas and appears mechanical in its reliance on a supernatural device. Sullivan, under pressure to write more serious music, says he longs for something that is "probable" and involves "human interest", and is not dependent on magic. Gilbert sees nothing wrong with his libretto and refuses to write a new one, which results in a standoff. The impasse is resolved after Gilbert and his wife visit a popular exhibition of Japanese arts and crafts in Knightsbridge, London. When the katana sword he purchases there falls noisily off the wall of his study, he is inspired to write a libretto set in exotic Japan. Sullivan likes the idea and agrees to compose the music for it.
Gilbert, Sullivan and Carte work to make The Mikado a success, and many glimpses of rehearsals and stressful backstage preparations for the show follow: Cast members lunch together before negotiating their salaries. Gilbert brings in Japanese girls from the exhibition to teach the ladies' chorus how to walk and use fans in the Japanese manner. The principal cast react to the fittings of their costumes designed by C. Wilhelm. The entire cast object to Gilbert's proposed cut of the title character's Act Two solo, "A more humane Mikado," which persuades the playwright to reconsider. The actors face first-night jitters in their dressing rooms. Finally The Mikado is ready to open. As usual, Gilbert is too nervous to watch the opening performance and paces the streets of London. Returning to the theatre, however, he finds that the new opera is a resounding success.
- "If You Give Me Your Attention" - Grossmith and Chorus
- "This Helmet, I Suppose" - Temple and Chorus
- "The Lost Chord" - Sullivan, Fanny and Simmonds
- "Incantation" - Grossmith, Lely, Leonora and Chorus
- "But Soft... / Why, Where Be Oi?" - Grossmith, Lely, Leonora and Chorus
- "Behold! the Lord High Executioner" - Grossmith and Chorus
- "A Wand'ring Minstrel, I" - Lely
- "Three Little Maids from School Are We" - Leonora, Jessie and Sybil
- "A More Humane Mikado" - Temple and Chorus
- "Mi-Ya-Sa-Ma" - Temple, Rosina and chorus
- "The Criminal Cried As He Dropped Him Down" - Grossmith, Jessie and Barrington
- "The Mikado Finale, Act Two" - Chorus
- "The Sun Whose Rays Are All Ablaze" - Leonora