Who is Winston Churchill from Winston Churchill: A Penguin Life and what is their importance?

Since Winston Churchill: A Penguin Life is a biography of Winston Churchill, he is obviously its most important character. In the book, nearly all aspects of Churchill's life are examined from his lineage to the events following his death. Little about Churchill is left unexamined.

Churchill's character traits come in for particularly close scrutiny; the most interesting and valuable part of studying Churchill seems to be understanding how he perseveres, despite physical ailments, an abiding depression and a severe level of stress that would have done in most normal men. Not only does he keep himself together, but he does so while inspiring a nation to fight against the most powerful military force in the world and arguably against one of the most powerful military forces in history.