The Crown star, 39, who had been nominated for Best Supporting Actress for the movie, stunned as she attended the late night bash in a gorgeous white lace gown.
She failed to pick up the gong in her nominated category, Best Supporting Actress, at the BAFTA Film Awards at the Royal Festival Hall on Sunday evening.
The English actress and activist, 37, looked striking as she stepped out for the star-studded party at private members club Annabel s in London following the ceremony.