Erich Kleiber
Away from Covent Garden, Shacklock appeared in opera in Berlin with Erich Kleiber, and sang in oratorio, notably as the angel in "The Dream of Gerontius" with Sir John Barbirolli. She was also a regular at Last Night of the Proms with Sir Malcolm Sargent, celebrated for her singing of "Rule, Britannia!" She also performed in Argentina as Octavian in "Der Rosenkavalier", with Birgit Nilsson as the Marschallin.