Portman is also the front-runner for the Oscar. The top British film awards and the Oscars have been aligning fairly closely in recent years.
She was in competition with Annette Bening and Julianne Moore, who costarred in "The Kids Are All Right," Noomi Rapace for "The Girl With the Dragon Tattoo" and Hailee Steinfeld for "True Grit."
The awards, presented by the British Academy of Film and Television Arts, were handed out in a ceremony at the Royal Opera House, Covent Garden, London.
-- Susan King
Photo: Natalie Portman in "Black Swan." Credit: Reuters