The state hands a prison warder the mail of the most famous prisoner in South Africa and orders him to read every line of it. Bille August's 2007 drama takes the long confinement of Nelson Mandela and tells it from the other side of the bars, through James Gregory, the censor officer who guarded him for close to twenty years.

Joseph Fiennes plays Gregory as a product of his country's laws before he is anything else, a man who arrives at the posting certain of what he has been taught. Dennis Haysbert plays Mandela with a stillness that gives the film its centre of gravity. Diane Kruger plays Gloria Gregory, whose marriage and household carry the cost of her husband's work, and the film gives that domestic pressure real screen time instead of leaving it in the background.

The script comes from Gregory's own memoir, Goodbye Bafana: Nelson Mandela, My Prisoner, My Friend, so the relationship reaches the screen as he told it. August directs in a sober register: few flourishes, long stretches of institutional routine, the apartheid state present in paperwork, orders and locked doors more than in speeches. The film reached United States audiences under a second title, The Color of Freedom.

It suits viewers who want the period approached through one ordinary functionary rather than through the leaders, and who can sit with a slow, plain, unsentimental vantage on twenty years of a life spent behind a door.