Written by Misan Sagay, this British historical drama is getting the “inspiring true story” treatment, though the inspiring parts aren’t true and the true parts aren’t inspiring. Dido Elizabeth Belle was the illegitimate child of an African woman and a white captain in the Royal Navy; deposited at the estate of her uncle, the esteemed jurist William Murray, Earl of Mansfield, she grew to young adulthood in social limbo, too low to dine with the family but too high to dine with the servants. Sagay turns her plight into a Jane Austen-style romance involving both sincere and scheming suitors, which allows the writer to unpack the social attitudes of the time. Her invented narrative works much better than the ensuing legal drama based on the 1781 Zong massacre, in which British slave traders tossed their sick slaves overboard; Murray ruled on the case as lord chief justice, and though the verdict is presented here as a blow against slavery, it was really a more mundane question of insurance law. Amma Asante directed; with Emily Watson, Miranda Richardson, Gugu Mbatha-Raw as the title character, and Tom Wilkinson in a strong performance as Murray.