A number of cultural institutions – including the BBC, Bafta and the Oscars – are under scrutiny for the whiteness of their repertoires and personnel. But theatre, though far from perfect, has a relatively better record on racial diversity, as is shown by the simultaneous London opening  of plays that find, in the history of African-American entertainment, major roles for black performers.Ma Rainey’s Black Bottom launched the reputation of August Wilson (1945–2005), who stands with Eugene O’Neill, Tennessee Williams, Arthur Miller and David Mamet among the most significant American dramatists to emerge in the twentieth century, each decade of which is represented by one of the plays in Wilson’s “Pittsburgh Cycle”.Taking its title from a