Once Upon a Time in Harlem, completed by relatives of William Greaves after his death, showcased at Cannes Once Upon a Time in Harlem, completed by relatives of William Greaves after his death, showcased at Cannes In 1969, the pioneering documentarian William Greaves wrote of his fury over the racially degrading stereotypes that white film producers threw up on American screens. “It became clear to me that unless we black people began to produce information for screen and television there would