It was an enjoyable movie, though the beginning courtship felt rather vague about how long they had been dating before Seretse proposed to Ruth. Once engaged, they face strong opposition from both Seretse's uncle and Ruth's father, along with the British Government itself. Bechuanaland is a British protectorate, so under the guise of preventing a civil war between Seretse and his uncle, the British bureaucrats try to keep him off his throne. Britain's real motive is to avoid offending South Africa, with its new apartheid policies; the prime minister argues that they need South Africa's uranium and gold, so they must exile Seretse. He and Ruth resist the machinations, but end up separated as they each try to stir public outrage to reverse the exile. Ruth was not welcomed at first by Seretse's sister and his aunt, but slowly they warm up to her and help her out, especially when she has to face pregnancy and childbirth alone.
Meanwhile, Seretse keeps making their case in England, with the help of a reporter and a sympathetic government official. I was surprised to learn that Winston Churchill even spoke out, claiming that he would end the exile if he was elected. When Churchill does win, though, he instead exiles Seretse for life! So apparently the campaign promise was all politics, and not sincere. Contrast that with the community-based kgotlas meetings, and the Bechuanaland government seems more respectable and honest.
There is a secret "Harringdon report" that Seretse is looking for, as well as an American mining company searching for diamonds on their land. A lot of political intrigue. Then Ruth finally gets to reunite with Seretse and her family in England, while Seretse works out a way to make up with his uncle to end the stand-off. Ultimately Seretse gives up the throne and argues that Bechuanaland should become a democracy and seek independence from Britain. It's a moving film, and David Oyelowo delivers some fine, impassioned speeches about leadership, freedom, and not going along with segregation.