Sienna Miller admits she isn't a "perfect person".

The 29-year-old actress - who is engaged to actor Jude Law for the second time after rekindling their romance in 2009, three years after they separated - insists her profession doesn't mean she should be judged for the decisions she makes in her personal life.

Sienna - who has previously dated actors Rhys Ifans and Balthazar Getty - told the Daily Mail newspaper: "I didn't know actors were supposed to be perfect people."

One aspect of her professional life which Sienna is looking forward to is returning to the stage in London to star in Terence Rattigan's 'Flare Path'- in which she plays a former actress caught in a love triangle - because it is such understated drama.

She said of the dialogue: "Its stiff upper lip. And that stiff upper lip hides characters'true feelings. "

Sienna also said the play's director, Trevor Nunn, had given her great advice practicing for the show.

She explained: "Once we're in the rehearsal room there's no one like Trevor to tell a story like this, and to uncover the subtext."

Rehearsals for the play begin at the end of January, with the opening night on March 10.