A United Kingdom is a powerful testament to the defiant and enduring love story of Seretse Khama, King of Bechuanaland (modern Botswana) and Ruth Williams, the London office worker he married in 1948 in the face of fierce opposition from their families and the government of the time. Director Amma Asante follows her previous film Belle with another elegant, impassioned drama that also reveals a painful episode in the history of British race relations and imperial politics. 

At a London dance, there is an immediate spark of attraction when the erudite and dashing Seretse (David Oyelowo) meets the independent-minded Ruth (Rosamund Pike). Ignoring the opposition of friends and family, they plunge into a whirlwind romance that leads rapidly to marriage. Reality sets in when, having completed his studies, Seretse has to return to Africa to assume his duties as King. Their interracial union is seen as a slap in the face both to Malan’s apartheid-riven South Africa and to the royal traditions of Seretse’s own people. As the international diplomatic crisis escalates, the British Government sets out to do everything in its power to drive the couple apart.