A United Kingdom

Based on a powerful true story from the late 1940s, this drama is packed with present-day resonance as it explores a relationship that sparks intense social and political fallout. And it's made properly engaging with central roles beautifully played by David Oyelowo and Rosamund Pike. So it's a shame that the screenplay is so simplistic, failing to generate any momentum in the story with its awkward structure and paper-thin side characters.

It opens in 1947, as Seretse Khama (Oyelowo) has spent 20 years of his life studying in London and is ready to return to Bechuanaland (now Botswana) to take his rightful place as king. But he has fallen in love with white, working-class Englishwoman Ruth (Pike), and they decide to return to Africa together. This causes a crisis for Seretse's uncle Tshkedi (Vusi Kunene), who has been ruling the country while Seretse was away. And there's even more fierce resistance from the British colonial officials (including Jack Davenport and Tom Felton), who refuse to allow the couple to live together in Bechuanaland because a mixed-race marriage undermines the UK's acceptance of South Africa's policy of Apartheid. So they exile Seretse from the country and manipulate the situation to Britain's political benefit. But Ruth stays and fights on.

The film chronicles this astonishing battle with a fascinating attention to detail, although screenwriter Guy Hibbert struggles to avoid repetition as the events shift between Africa and London, leaving main characters off the screen for what turns out to be years at a time. Meanwhile, the British are portrayed as moustache-twirling villains who lie and conspire to undermine the government of Bechuanaland. A bit more complexity might have made the situation compelling on-screen.

Instead, the focus is on the twisty romance between Seretse and Ruth, which is so well-played that it's strongly moving in all the right ways. Both Oyelowo and Pike bring layers of intelligence, emotion and yearning that give the film a proper kick. And there's solid support from Kunene, as well as Terry Pheto and Laura Carmichael (as Seretse's and Ruth's sisters, respectively), plus a nicely subtle turn from Nicholas Lyndhurst as Ruth's father.

The film is beautifully directed by Amma Asante (Belle) to capture the period as well as the contrasts between life in Britain and Africa. So the personal side of this story is hugely involving. And if Hibbert had written the political elements without moralising through the conflict and simplifying the people, the film might have expressed its bigger central themes much more effectively.

Watch the trailer for A United Kingdom: