During his Covent Garden tenure, Davis returned to the BBC Symphony Orchestra as principal guest conductor from 1971 to 1975, and held the same post with the Boston Symphony Orchestra from 1972 to 1984. In 1977, he became the first English conductor to appear at Bayreuth, where he conducted the opening opera of the festival, "Tannhäuser". Despite the Bayreuth habitués' suspicion of newcomers, his "Tannhäuser" was "highly successful". He debuted at the Metropolitan Opera, New York City, in 1967 with "Peter Grimes", the Vienna State Opera in 1986 and the Bavarian State Opera in 1994.