Her English engagement at the Royal Italian Opera, in 1848, began with the performance of _Amina_ in "La Sonnambula," and created a great sensation, for she was about to contest the suffrages of the public with a group of the foremost singers of the world, among whom were Grisi, Alboni, and Persiani. Mme. Viardot's nervousness was apparent to all. "She proved herself equal to Malibran," says a writer in the "Musical World," speaking of this performance; "there was the same passionate fervor, the same absorbing depth of feeling; we heard the same tones whose naturalness and pathos stole into our very heart of hearts; we saw the same abstraction, the same abandonment, the same rapturous awakening to joy, to love, and to devotion. Such novel and extraordinary passages, such daring nights into the region of fioriture, together with chromatic runs ascending and descending, embracing the three registers of the soprano, mezzo-soprano, and contralto, we have not heard since the days of Malibran." Another critic made an accurate gauge of her peculiar greatness in saying: "Mme. Viardot's voice grows unconsciously upon you, until at last you are blind to its imperfections. The voice penetrates to the heart by its sympathetic tones, and you forget everything in it but its touching and affecting quality. You care little or nothing for the mechanism, or rather, for the weakness of the organ. You are no longer a critic, but spellbound by the hand of genius, moved by the sway of enthusiasm that comes from the soul, abashed in the presence of intellect." The most memorable event of this distinguished artist's life was her performance, in 1849, of the character of _Fides_ in "Le Prophete." No operatic creation ever made a greater sensation in Paris. Meyerbeer had kept it in his portfolio for years, awaiting the time when Mme. Viardot should be ready to interpret it, and many changes had been made from time to time at the suggestion of the great singer, who united to her executive skill an intellect of the first rank, and a musical knowledge second to that of few composers. At the very last moment it is said that one or more of the acts were entirely reconstructed, at the wish of the representative of _Fides_, whose dramatic instincts were as unerring as her musical judgment. No performance since that of Viardot, though the most eminent singers have essayed the part, has equaled the first ideal set by her creation from its possibilities.