Sapphire

Sapphire is a movie starring Nigel Patrick, Yvonne Mitchell, and Michael Craig. The murder of a young woman in London exposes deep racial tensions and prejudices inherent in the area.
Two Scotland Yard detectives investigate the murder of a young woman of mixed race who had been passing for white. As they interview a spate of suspects -- including the girl's white boyfriend and his disapproving parents -- the detectives wade through a stubbornly entrenched sludge of racism and bigotry.