He made his Broadway debut in The Promise (1965). He went on to receive the Tony Award for Best Actor in a Play for his role as Antonio Salieri in Amadeus (1980). He was further nominated for Ian McKellen: Acting Shakespeare (1984). He returned to Broadway in Wild Honey (1986), Dance of Death (1990), No Man's Land (2013), and Waiting for Godot (2013), the later being a joint production with Patrick Stewart.
