A United Kingdom is based on extraordinary true events. In 1947, Seretse Khama (David Oyelowo), the King of Botswana, met Ruth Williams (Rosamund Pike), a London office worker. They were a perfect match, yet their proposed marriage was challenged not only by their families but by the British and South African governments. The latter had recently introduced the policy of apartheid and found the notion of a biracial couple ruling a neighboring country intolerable. South Africa threatened the British: either thwart the couple or be denied access to South African uranium and gold and face the risk of South Africa invading Botswana.