This volume investigates the internal operations and strategic decision-making processes of British counter-espionage during the height of World War II. Nigel West, a noted historian and expert on intelligence services, provides the necessary context to interpret the raw entries of Guy Liddell, the Director of Counter-Espionage for MI5. By presenting these primary source documents, the book argues that Liddell’s daily observations offer a unique, unfiltered perspective on the administrative and operational challenges faced by British intelligence between 1939 and 1945.

Experts and historians consider this collection a foundational resource for understanding the mechanics of British intelligence during the Second World War. Readers frequently note the density of the prose and the specialized nature of the content, which serves as a vital reference for scholars of 20th-century espionage.