Book excerpt: A TV tie-in edition of The Code Book filmed as a prime-time five-part Channel 4 series on the history of codes and code-breaking and presented by the author. This book, which accompanies the major Channel 4 series, brings to life the hidden history of codes and code breaking. Since the birth of writing, there has also been the need for secrecy. The story of codes is the story of the brilliant men and women who used mathematics, linguistics, machines, computers, gut instinct, logic and detective work to encrypt and break these secrect messages and the effect their work has had on history.