All her life, she knew who she was. Now the roles she had embraced — mother, wife, performer — have her asking, "Am I any of those things? And if I'm not, who am I?"

If anyone did not expect to have a midlife crisis, it was Emma Thompson. Being quite sure about things has been a central organising principle of her life. It has informed most every character she has played.

The kindly aristocrat in Howards End. The lovelorn housekeeper in The Remains of the Day. The bonneted sister of Sense and Sensibility. The batty Hogwarts professor, the warty