I don’t mind admitting that, until Lorraine Hansberry’s play “Les Blancs” opened at the National this month, I’d never even heard of it. After sitting through Yaël Farber’s production last night, I don’t feel quite so guilty. The London critics greeted this revival with a blast of four-star raves, but in all honesty it’s a brave but deeply flawed piece inhabited by one-dimensional characters who never seem more than expressions of different political points of view. At a mission hospital, colonists confront “natives”, a revolutionary spars with a liberal, and — always a bad sign — a visiting journalist looks on, taking notes for a story. Hansberry, who didn’t finish the work before her tragically early death (her husband Robert Nemiroff adapted the final text) is said to have wanted to draw on Greek classical drama. You can see the reference points clearly enough in the measured pacing and the declamatory dialogue. Unfortunately, in Hansberry’s unnamed country, which has elements of Kenya’s Mau-Mau revolt mixed in with hints of Fanon and Apartheid South Africa, the storyline and the dialogue are politely predictable. Even in 1970, when the play was first staged on Broadway, it’s hard to believe that it seemed particularly incendiary. While the performances at the National are never less than immaculate, the actors often seem in danger of being upstaged by the modish revolving set and the ritualistic music and chanting. A huge amount of effort has gone into the staging, yet it’s still not enough to camouflage the fatal lack of substance underneath. Reading up on the play this afternoon, I discovered a Guardian review of a Royal Exchange revival in 2001 which praised the production but described the script as “clunky” and “schematic”. I’m relieved to see I’m not alone.