The kingdom in question, of course, is not the one within the British Isles, but Botswana – or Bechuanaland, as it was known in the post-war years when crown prince Seretse Khama (David Oyelowo) came to London to study, and fell unexpectedly in love with shopkeeper's daughter Ruth Williams (Rosamund Pike). Their subsequent marriage scandalised not just the tabloid-buying public but the British civil service, the tribespeople of Botswana and – most dangerously – the government of neighbouring South Africa, whose new apartheid laws enshrined the separation of the races into law.
'Belle' director Amma Asante's tribute to this unlikely couple is exactly the film you imagine it's going to be: handsome, honey-coloured and morally simplistic. It's a story of forbidden romance and political intrigue in far-flung locations. Not that this is necessarily a bad thing: Asante's confidence behind the camera, coupled with a solid script from TV veteran Guy Hibbert and a pair of committed central performances, ensure that 'A United Kingdom' is never less than entertaining, and at times genuinely moving.
The strongest sequences see Seretse exiled back to the UK, as the post-war Labour government endeavour to take back control of an increasingly wayward protectorate and pacify the South Africans in the process (British lefty audiences are bound to raise a smile when a young upstart MP arrives at the prince's door with a cheery 'hello, I'm Anthony Benn!'). Asante and Hibbert aren't afraid to dig into the corrupt machinations of colonial rule, and it's both fascinating and timely as Khama's authority is betrayed time and again by a series of smarmy, upper-crust movers and shakers. Oyelowo exudes quiet dignity but he can belt out a rousing speech when he needs to, and Pike genuinely seems to be enjoying herself as Ruth transforms, little by little, from shrinking violet to jeep-driving, baby-swaddling, authority-baiting queen of the veldt.
But in the main 'A United Kingdom' is just a little too cosy and sentimental for its own good. Shots of giraffes romping majestically across the plain bring a sense of picturesque National Geographic naivety, and given the scorching African heat it's remarkable how little our glamorous heroine seems to perspire.