British Intelligence in the Second World War: Volume 4, Security and Counter-Intelligence: Security and Counter-intelligence v. 4. The fourth volume analyzes the contribution made by intelligence to the work of the authorities responsible for countering the threats of subversion, sabotage and intelligence gathering by the enemy in the United Kingdom and British territories overseas, and neutral countries. It describes the evolution of the security intelligence agencies between the wars and the security situation in September 1939 and reviews the arguments about security policy regarding enemy aliens, Fascists and Communists in the winter of 1939–1940 and during the Fifth Column panic in the summer of 1940.