Balm to the soul for liberal-minded theatregoers, Aaron Sorkin's stately adaptation of Harper Lee's American classic makes a welcome return to the West End. It's a courtroom drama, a coming-of-age tale and a lesson in decency, in which small-town lawyer Atticus Finch defends a black man wrongfully accused of rape in Alabama in 1934. Sorkin, the creator of The West Wing and writer of The Social Network among much, much else, excels at smooth talk and moral certitude.