Born in Peckham, she studied with Audrey Langford, and became a member of the Royal Opera House chorus in 1949. She made her debut as a soloist on 5 July 1955 as the Page in Salome, followed by Cherubino in Le nozze di Figaro, and later roles included Dorabella in Così fan tutte, Marina in Boris Godunov, Preziosilla in La forza del destino, Eboli in Don Carlos, Amneris in Aida, and sang the title role in Carmen, amongst others. Beginning in 1957, she became a regular guest at the Glyndebourne Festival, notably as Charlotte in Werther and Octavian in Der Rosenkavalier.
Noticed and encouraged by Georg Solti, she began adding Wagner roles to her repertoire, notably Waltraute and Fricka in Die Walküre, the second of which she recorded for DG under Herbert von Karajan). Other included major roles in Tristan und Isolde, Venus in Tannhäuser (opera), and Kundry in Parsifal. Under Colin Davis' guidance, she also became an illustrious interpreter of Berlioz's works, singing both Didon and Cassandre in Les Troyens, and Marguerite in La damnation de Faust, which she also recorded for him.
On the international scene, she appeared at the Paris Opéra, the Aix-en-Provence Festival, at La Scala in Milan, the Vienna State Opera, the Salzburg Festival, the Metropolitan Opera, and the San Francisco Opera. In 1962, she created the role of Andromache in Michael Tippett's King Priam, and in 1976 created The Emperor in Hans Werner Henze's We Come to the River.
Although not associated with the bel canto repertoire, she recorded in 1966, the role of Agnese in Beatrice di Tenda, opposite Joan Sutherland and Luciano Pavarotti, under Richard Bonynge, and appeared as Adalgisa in Norma, opposite Montserrat Caballé and Jon Vickers, in the famous production, recorded on DVD, at the Théâtre Antique d'Orange in 1974.
One of her many distinguished roles was as Charlotte in Massenet's Werther. By chance, the BBC Radio 3 broadcast of that opera on 8 July 1979 captured for posterity her portrayal because she had stood in at the last minute for the indisposed Teresa Berganza and partnered Alfredo Kraus in one of his signature roles.