The Shadowlands playwright talks about C S Lewis, love, pain and being a writer It is 30 years since Shadowlands, William Nicholson's much-loved play about C S Lewis's unexpected love affair with Joy Gresham, an American poet, was first seen on stage. The famous academic and author of the Narnia books, apparently content in his male world of Oxford high tables and intellectual cut-and-thrust, was transformed by his m…