Like many great actors, Emma Thompson was drawing from personal experience to inform her performance.
You can watch the scene from Love Actually below to see the Oscar-winning actress deliver some impressive method acting.
Emma Thompson was once married to actor/director Kenneth Branagh, who cheated on her with Helena Bonham Carter.
So in this scene, she knew exactly how her character felt and simply had to think of her own experience to conjure the emotion necessary for the scene.