This is the first history and analysis of the intelligence and espionage activities of the regime of Charles II (1660–85). It is concerned with the mechanics, activities and philosophy of the intelligence system which developed under the auspices of the office of the Secretary of State and which emerged in the face of the problems of conspiracy and international politics. It examines the development of intelligence networks on a local and international level, the use made of the Post Office, codes and ciphers, and the employment of spies, informers and assassins. The careers of a number of spies employed by the regime are examined through a series of detailed case studes. The book provides a balanced portrait of the dark byways of Restoration politics, particularly in the 1660s and 1670s, and fills an important gap in the current literature.