The year is 1948. Apartheid has just begun. Race relations in London are far from positive. The British government, in classic 1948 British government form, is up to something shady in the developing countries of South Africa.

Despite all of this, Sir Seretse Khama and Ruth Williams Khama are remarkably, inexplicably in love.

A United Kingdom, based on the true story depicted in Susan Williams’ book Colour Bar, is the latest British blockbuster to hit theaters. The romantic drama is Amma Asante’s third directorial project, her last being the period drama Belle in 2013.

The film stars Rosamund Pike as Williams, a white London office worker who quickly and deeply falls in love with Seretse Khama (David Oyelowo), who is the current heir to the chieftainship of the Bangwato people in Bechuanaland, a southern African nation that would later become Botswana. The two decide to get married. Blinded by an intense adoration of each other, neither predicts the hardships that will come as they attempt to navigate race relations in both of their countries. The British and South African governments present substantial roadblocks as the pair tries to salvage their relationship and fight for the wellbeing of the people of Bechuanaland, who largely don’t approve of their soon-to-be queen.

Pike and Oyelowo play off each other with seemingly authentic ease. Their chemistry is charming and believable and they succeed in their portrayal of a couple so enamored with each other, they’re willing to sacrifice almost anything. It’s a funny turn for Pike, who we last saw on Gone Girl playing a wife character with such a deep hatred for her husband she wants him dead.

The cast has some standouts aside from the starring couple. Most notably, Abena Ayivor, who plays Seretse Khama’s aunt, Ella Khama. In what is by far the best monologue of the film, Ella confronts Ruth about the realities of trying to become the face of a nation that not only does not want her, but has been drastically let down after waiting years to have a queen that represents the people, not one that has been shipped over from London. Ayivor dominates this scene with such measured intensity, and it’s a shame she doesn’t make many other appearances in the film.

The pacing of the film is probably its most notable flaw. The first 15 minutes are almost exclusively exposition, as the leading couple are rushed into a relationship, seemingly so the plot can reach its more disastrous aspects in time to fit it all in without seeming long or tedious. And yet, the second half still seems, well, long and tedious. The film isn’t incredibly long, running a little under two hours — but it somehow manages to feel much longer. Granted, this effect is sometimes positive, as it works to drive home just how long it took the Khamas to reunite. But mostly the second half tends to sloth its way to an ending most will see coming the whole time.

A United Kingdom is best when it is capturing raw emotion, whether it’s the broken tones of Ruth’s voice as she begs Seretse to return to her, or the joyful songs of the women of Bechuanaland. Even through its more exhaustingly paced portions, it’s these emotions that drive the film.