LONDON (Reuters) - Author Dan Brown did not copy material from an earlier book when he wrote "The Da Vinci Code", his best-selling religious thriller at the center of a copyright case, a lawyer told London's High Court on Tuesday. With over 36 million copies of his novel in circulation and a major Hollywood adaptation due for release in May, the stakes are high in a case brought against Brown's British publishers by historians Michael Baigent and Richard Leigh. In opening arguments for the defense, publisher Random House said that much of the "central theme" of "The Holy Blood, and...