Question: How many operas did the person who wrote the music for Haddon Hall make?

Context articles: George Vernon (MP for Derby and Derbyshire)
Dorothy Vernon
Haddon Hall (opera)
Sydney Grundy
Arthur Sullivan
Dorothy Vernon of Haddon Hall (film)
Nether Haddon
Grace, Lady Manners
Haddon Hall
Gertrude Lightstone Mittelmann

George Vernon (c. 1508 – August 31, 1565) was and a prosperous and hospitable landowner and MP in Derbyshire, who came from a long line of wealthy landowners.
 His family seat was at Haddon Hall, England's best preserved medieval manor house and today a major tourist attraction.
 He was a Member (MP) of the Parliament of England for Derbyshire in 1542.
Dorothy Vernon (1544 – 24 June 1584), the younger daughter of Sir George Vernon, was the heiress of Haddon Hall, an English country house in Derbyshire with its origins in the 12th century.
 She married John Manners in 1563.
 The couple's descendants, the Dukes of Rutland, continue to own Haddon Hall.
 A legend grew up in the 19th century that Vernon and Manners eloped, and a number of novels, dramatisations and other works of fiction have been based on the legend.
Haddon Hall is an English light opera with music by Arthur Sullivan and a libretto by Sydney Grundy.
 The opera, set at the eponymous hall, dramatises the legend of Dorothy Vernon's elopement with John Manners, resetting the tale in the 17th century.
Sydney Grundy (23 March 1848 – 4 July 1914) was an English dramatist.
 Most of his works were adaptations of European plays, and many became successful enough to tour throughout the English-speaking world.
 He is, however, perhaps best remembered today as the librettist of several comic operas, notably "Haddon Hall".
Sir Arthur Seymour Sullivan MVO (13 May 1842 – 22 November 1900) was an English composer.
 He is best known for his series of 14 operatic collaborations with the dramatist W. S. Gilbert, including "H.M.S. Pinafore", "The Pirates of Penzance" and "The Mikado".
 His works include 23 operas, 13 major orchestral works, eight choral works and oratorios, two ballets, incidental music to several plays, and numerous hymns and other church pieces, songs, and piano and chamber pieces.
 The best known of his hymns and songs include "Onward Christian Soldiers" and "The Lost Chord".
Dorothy Vernon of Haddon Hall is a 1924 silent historical drama directed by Marshall Neilan and starring Mary Pickford.
 The script by Waldemar Young was based upon the 1902 novel "Dorothy Vernon of Haddon Hall" by Charles Major.
Nether Haddon is a sparsely populated village and civil parish in Derbyshire, England.
 It is immediately downstream along the River Wye from the small town of Bakewell and much of its land is owned by Haddon Hall, a medieval and Tudor building largely rendered in stone.
 The population of the village is included in the civil parish of Over Haddon.
Grace, Lady Manners was an English noblewoman who lived at Haddon Hall near Bakewell, Derbyshire.
 She founded Lady Manners School in 1636.
Haddon Hall is an English country house on the River Wye near Bakewell, Derbyshire, one of the seats of the Duke of Rutland.
 It is currently occupied by Lord Edward Manners (brother of the current Duke) and his family.
 In form a medieval manor house, it has been described as "the most complete and most interesting house of [its] period".
 The origins of the hall date to the 11th century.
 The current medieval and Tudor hall includes additions added at various stages between the 13th and the 17th centuries.
Gertrude Lightstone Mittelmann (also Gertrude Mittelmann, and Mrs. Jesse Mittelmann) born in New York City, 1907, was an American concert pianist.
 The daughter of a well-known New York surgeon, Dr. Abraham (Albert) Lightstone (1874–1955), she was one of the first women radio show hosts, notably at WQXR-AM 1550 KC (Interstate Broadcasting Company).
 She gave one of her first American concerts at Haddon Hall in 1928.
 Vinyl and metal record albums were recorded of her performances as a symphonic concert pianist for various orchestras and recitals as a solo artist.
 In addition, many of her broadcasts as a radio host were recorded on record albums.
 She participated in numerous cultural and community activities.