Like its protagonists, A United Kingdom, directed by Amma Asante, always retains its calm and dignity.

A United Kingdom (12A)

***

The title might lead you to expect an unflinching examination of our present day problems and divisions, but this offers instead a look back at our past failings. That is the British way.

It is the late 1940s, and Seretse Kwama (David Oyelowo) is an African prince being educated in England so that he can go back to lead his people in the British Protectorate of Bechuanaland (what is now Botswana) and take over from his uncle (Vusi Kunene).

But when he marries a white English woman (Rosamund Pike) the hostile reaction to Kwama's decision is instant. His family shuns him and the British, under pressure from the apartheid regime in South Africa, exile him.

He has to fight to get back to his country and unite his people.

Like its protagonists, the film, directed by Amma Asante, who previously helmed 2013's Belle and 2004's A Way of Life, always retains its calm and dignity.

The Richard Attenborough tradition hangs over the film: there are stirring speeches and shows of fortitude. Like any good British occasion the whole thing runs smoothly and to time. Its saving grace is a curiosity about the wider world beyond the central stand against intolerance.

Jack Davenport and Tom Felton are there to fulfill the roles of the superior, condescending British diplomats, but the other bad guys do get to put their side of the story.

Clement Attlee explains to a young Tony Benn why it is was a financial necessity for an impoverished post war Britain not to alienate resource rich South Africa; when he returns the uncle reminds him that he was sent away to prepare to lead his people, to put his people before his own happiness.