During the 1990s WNO made its Proms debut , with a complete performance of Mozart 's Idomeneo , conducted by Mackerras in 1991 . The company played three short seasons at the Royal Opera House , Covent Garden in the mid @-@ 1990s , featuring Tristan und Isolde and La favorita in 1993 , The Yeomen of the Guard in 1995 , and The Rake 's Progress and the jubilee double bill of Cavalleria Rusticana and Pagliacci in 1996 .