Sir Francis Walsingham (1532-1590), an adviser to Queen Elizabeth I, is generally accepted to be the head of the first intelligence agency in the West. He is credited with personally developing a number of aspects of tradecraft, such as invisible inks and clandestine mail opening.
In 2006, a report from an English diplomat, Dr. Valentine Dale, to Walsingham was exhibited by the Library of Congress. It was a diplomatic input to his broader program to provide intelligence of the Spanish Armada.
He developed a comprehensive collection plan and employed a network of agents throughout Europe to gather information. He never blindly trusted any one source, using multiple agents against the same target. As the Armada preparations came to a head, Walsingham commissioned naval reconnaissance missions of key Spanish ports, and although his work provided strategic warning to the crown and the Royal Navy, contrary winds prevented tactical warning.
- Kahn, David, The Codebreakers: the Story of Secret Writing (Revised, 1996 ed.), Scribners, p. 119
- Hans P. Kraus (2006), Sir Francis Drake: A Pictorial Biography -- The Invincible Armada, Library of Congress
- John R. Arpin (Summer, 2006), "(book review) Budiansky, Stephen. Her Majesty's Spymaster: Elizabeth I, Sir Francis Walsingham, and the Birth of Modern Espionage", Naval War College Review