When the history of British codebreaking is told, the story is often a men-only preserve. That perception completely ignores the fact that the vast majority of codebreakers were in fact women. And foremost among them was one who is largely unknown to the public, and whose activities were a secret even to her closest contacts – Emily Anderson. Anderson was a leading member of British intelligence for over three decades. She played key roles in both World Wars, worked in Bletchley Park and in the Middle East, and was reckoned among the top three female codebreakers in the world. Her work coincided with her other great love – music. She is famous in musicology circles as being the first to effectively decipher the letters and diaries of Mozart and Beethoven. This narrative of her life places Emily Anderson at the forefront of great British codebreakers.