Drawing on private and previously classified documents, this definitive history of women's contributions to the intelligence services is the first authoritative account of the hidden female army of clerks, typists, telephonists, and secretaries who were the cornerstone of the British secret state across two world wars and beyond. To the undiscerning eye, they were secretaries, typists, personal assistants, and telephonists. But those innocuous job titles provided the perfect cover for what were in reality a range of complex technical, clerical, and occupational roles. Often overlooked and underestimated by outsiders, the women of British intelligence encoded, decoded, and translated enemy messages, wrote propaganda, and oversaw agents, performing duties as diverse as they were indispensable. Drawing on extensive research and unique access to family archives, Claire portrays many of these remarkable figures—including the brilliant, multi-lingual Lunn sisters, glamorous spy Olga Gray; and Jane Sissmore, MI5's first female officer—and reconsiders the priceless contributions they made.