Was born in Pontnewynydd, Wales, UK in 1936. Her mother died when Gwyneth was three years old and her father shortly before she learnt that she had been accepted as a student by the Royal College in London. After studying there and later at the Accademia Chigiana in Siena and at the International Opera Studio in Zürich, she received her first commitment in 1962/63 at Zürich Opera, where she initially celebrated successes in the mezzo discipline, holding her debut as Czipra in Johann Strauss’ The Gypsey Baron. A year later, she already performed her first soprano role, Amelia in Verdi’s Un ballo in maschera, likewise in Zürich. Many more major Verdi soprano roles were to follow a few years later, including at Covent Garden in London. Her international career began in the second half of the 1960s, reaching its absolute climax as Brünnhilde in the Bayreuth ‘Century’s Ring’, staged by Patrice Chéreau and conducted by Pierre Boulez in 1976. In the 1970s and 1980s, she set standards at the major opera houses throughout the world above all in Wagner and Strauss roles. In her later career, she sometimes moved to the character discipline, also appearing in the land of light entertainment, e.g. in Gilbert & Sullivan’s Pirates of Pensance at the Vienna Volksoper in 2002.