Penzance, The Guardian commented, "It is Valerie Masterson's Mabel that makes one revise ideas on D'Oyly Carte standards. It is a long time since the company had so strong a soprano lead." Other critics agreed: The Times criticised D'Oyly Carte vocal standards in 1968 but called Masterson and Kenneth Sandford "shining exceptions." She remained with D'Oyly Carte for five years, where her major roles were Mabel; Josephine in H.M.S. Pinafore; Phyllis in Iolanthe; Lady Psyche, and subsequently the title role, in Princess Ida; Yum-Yum in The Mikado; Elsie Maynard in The Yeomen of the Guard; and Casilda in The Gondoliers. She appeared as Yum-Yum in the company's 1966 film version of The Mikado. She left the company in 1969 but often returned for guest appearances. Opera career Masterson went on to become principal soprano with English National Opera, from 1971, singing a wide range of roles from Mozart to Wagner and Rossini to Puccini. Her successes there included Adèle in Rossini's Le comte Ory, Micaëla in Carmen, Violetta in La traviata and the title role in Massenet's Manon ("exquisitely sung and acted"). Her many other roles there included Woglinde and the Woodbird in the Ring and Sophie and the Marschallin in Der Rosenkavalier. She made her Royal Opera House, Covent Garden debut in 1974 and her French debut at Toulouse in 1975 as Manon. For three seasons, beginning in 1975, at the Aix-en-Provence Festival, she sang a variety of roles, including "a memorable Matilde in Elisabetta, regina d'Inghilterra". Other early roles included Mimì in La bohème and Pamina in The Magic Flute. She has sung in Strasbourg (Pamina), Rouen (Countess, Marriage of Figaro), and Toulouse (Violetta). There followed starring roles, over a career lasting more than 30 years, in major opera houses around the world. Her repertory extended from the earliest operas to late 20th century works. At Covent Garden she created the role of May in Hans Werner Henze's 1976 premiere of We Come to the River, and sang The Anne who Steals in Aulis Sallinen's 1984 opera The King Goes Forth to France, at the UK premiere on 1 April 1987. Of her 1983 Madame Lidoine in Dialogues des Carmélites, The Times wrote that Masterson "makes a sound so beautiful one wishes it could go on for ever. ... Life offers few pleasures like that of hearing Felicity Lott and Valerie Masterson singing on the same stage". She