Dramatic Character in the English Romantic Age

This was the age of the star. For the first time in the history of the theater, the playwright took second place to the actor; the interpretation of the role assumed primary importance in a assessing a performance. It was Mr. Kean's Hamlet first, and Mr. Shakespeare's second. What effects did this highly subjective, interpretive emphasis have on the drama? Where did it originate and how did it evolve?