Wilde Sapte has dealt the final blow to objectors who called a rural opera a "noise nuisance".
Environment Secretary John Gummer has granted the Garsington Opera Festival planning permission for seven years after a lengthy inquiry.
The opera, run by Leonard Ingrams, brother of Bernard Ingrams and based at historic Garsington Manor in Oxfordshire, raised protests from some residents after its first festival in 1989. Ingrams was convicted of causing a "noise nuisance" in 1994, but Wilde Sapte helped quash the conviction in April 1995.
South Oxfordshire District Council would only give the opera planning permission for a year at a time, but it wanted seven years' permission.
Wilde Sapte partner Brian Smith handled the inquiry and instructed Jeremy Sullivan QC, South Oxfordshire instructed Richard Drabble QC.