Biographical films of real-world figures and historical films have an identical Achilles heel. If they’re presented with an aura of subdued seriousness and a shortage of compelling drama, they devolve into “this happens and then that happens” catalogs of information. No matter how important the subject matter might be, viewers need a thematic through-line and an absorbing psychological undercurrent. As a species, we’re guided more by feelings than data.

Which makes “A United Kingdom” a might-have-been. It makes no bones about attempting to turn a story of cross-cultural romance and international politics into a solid crowd-pleaser. But it doesn’t strike that irresistible spark. It’s good, but not good enough.

The narrative begins in London in 1947 and centers on the true story of Seretse Khama, a handsome African law student at Oxford University (David Oyelowo), and his English beloved, Ruth Williams (Rosamund Pike). It’s a postwar era of social and political antagonism.

The story’s fairy-tale dimension is that Seretse was a prince, next in line to rule Britain’s small colony of Bechuanaland (now known as Botswana). After they meet by chance, see a fine future together and marry, the pair’s union brings to light issues of race relations between Britain and its far-off colony.

Though Oyelowo’s Seretse is capable of battling London’s racist hooligans hand to hand, the newlyweds face deeper problems. Their courtship triggers hostility from all corners.

Ruth’s intolerant working-class parents are aghast that she would marry upward and outward in such an unconventional fashion. Britain’s political and diplomatic corps sees the scandalous situation endangering relations with their anti-Communist ally South Africa, which is in the process of instituting its racist apartheid policies. Even total strangers create ugly incidents on the streets of London, offended by the rarity of a black man with a white woman.

The situation does not improve when they relocate to Africa. Distrusting the motivation behind the marriage, Seretse’s clan fears it is part of a scheme by the British, who are interested in the area’s diamonds, to strengthen their grip on the region.

The film picks up legal battles and human topics similar to the civil rights love story “Loving,” a drama about the couple whose marriage helped to legalize interracial marriage in the U.S. But where “Loving” portrayed the daily life of its duo through unadorned authenticity, this veers to oversaturated sentiment.

Amid a steady swirl of forces conspiring to forbid or undo the marriage, the couple move through a range of traditional Harlequin Romance events, completing each task to the barest minimum standard. They face injustice, travel quaint landscapes, endure separation, turn disapproving adversaries into staunch friends and produce a new generation of tribal monarchs.

Hearing that news while they are continents apart during a period of exile gives Oyelowo the best moment in the movie. A golden-throated orator (you may recall his work as the Rev. Martin Luther King Jr. in “Selma”), he’s reduced here to almost speechless emotion, as the joy of fatherhood and the pain of being apart fuse before our eyes.

But Pike, who can perform like a consummate professional (in David Fincher’s thriller “Gone Girl”) or a department store mannequin (in almost everything else) is not at the top of her range. She’s better as a character actress than as a romantic lead. She behaves like a representative of icy moral virtue rather than a relatable human. Her English stiff upper lip looks numb. Which, in the end, is the problem with the safe script and this listless film. While the soundtrack tries to push us along in a kind of operatic sweep, the movie doesn’t dance to the proper beat.