Movies about great people tend to be, well, not so great. If you’re still enthused about the Oscar-winning Gandhi, my apologies. I’m not. There’s that rush to get everything in so that the essentials of characterization that often lie on the fringes get neglected or totally ignored. But don’t dump Mandela: Long Walk to Freedom on the scrap heap just yet. Biopic blight definitely afflicts this respectful, near-canonizing look at the life of Nelson Mandela, elected President of South Africa from 1994 to 1999 after serving 27 years in prison for his anti-apartheid politics. But in adapting Madela’s autobiography to the screen, director Justin Chadwick (The Other Boleyn Girl) and screenwriter William Nicholson (Gladiator) lucked out in finding a hell of an actor to play him. Idris Elba, the British producer, musician, rapper, DJ (under the name DJ Big Driis) and gifted actor who won justifiable raves as drug lord Stringer Bell on The Wire and as obsessed detective on the BBC’s Luther, grabs the role like a man possessed. It’s an astounding performance. Elba may not resemble the man he’s playing, but he gets the details right, from the singsong accent and shrewd image-making to the fire for change that drives him. Actors, from Morgan Freeman to Danny Glover, have played Mandela. But Elba, 41, brings out the vigor and strut of his youth as Johannesburg lawyer, activist, lover, and prime mover in the African National Congress. It’s there that Mandela meets first wife, Evelyn Mase (Terry Pheto). But it’s his second marriage to social worker Winnie Madikizela (Naomie Harris) that grabs our attention. Harris, who starred in Chadwick’s underrated The First Grader and played the new Moneypenny to Daniel Craig’s James Bond in Skyfall, digs into the role, even when the script does not. Winnie’s radicalization deserved more screen time. But we see her power thanks to the ferocity and feeling Harris brings to the role. Mandela: Long Walk to Freedom is a long slog of a movie that insists on hitting the high spots like a Wiki page, which leaves little room to investigate the political and personal changes that altered Mandela’s thoughts about violence and its uses. But in those moments when Elba shows the doubts, compromises and complications that make the man, we get glimpses of a life truly lived.