Seretse warns Ruth early that a long-term relationship will be difficult, because he is heir to the throne of the Bamangwato tribe, the predominant native population of Bechwanaland, and will soon return home to become king. Still, they continue a courtship, until Seretse asks Ruth to marry him, and she accepts.
The marriage is met with opposition on several fronts. These include Ruth's bigoted father (Nicholas Lyndhurst), Seretse's uncle Tshekedi (Vusi Kunene), who is also the tribe's regent, and the British government — which fears a rift with South Africa, which has recently instituted the apartheid laws that codified segregation of black from white for nearly half a century.
The Brits — embodied by the fictitious government official Sir Alistair Canning (Jack Davenport) and his local commissioner (Tom Felton) — throw up obstacles to Seretse's return to Bechwanaland, using the excuse of the rift between Seretse and his uncle to enforce British rule on the territory. The Brits, eager to assuage the South African government and maintain access to its gold and other resources, maneuver to have Seretse banished from his home country, separating him from Ruth and their baby daughter.
Director Amma Asante ("Belle") and screenwriter Guy Hibbert ("Eye in the Sky") have the difficult job of cutting through a mountain of bureaucratic intrigue to shape a compelling story. They find the thread in Seretse and Ruth's enduring love and their drive to be together even when politics and racism are trying to tear them apart.
Oyelowo, so memorable as Martin Luther King in "Selma," gives a powerful performance as the prince, tender as Ruth's paramour and dynamic as a rising ruler. Pike ("Gone Girl") particularly shines in scenes where Ruth overcomes resentment from the native women and works to embrace her new home's culture. Together, they make "A United Kingdom" a warm, welcoming story of love crossing all borders.