Invisible inks. Hollow heels. Hidden briefcase compartments. Microdot photography. All seemingly the stuff of spy thrillers, born of the imagination of writers such as Ian Fleming. But all are actual historical examples of espionage methods. Spies cannot conjure the tools of their craft out of thin air. No single person in the field can develop the technology required for a fake rock to store and transmit secret information to spies’ hand-held devices, as a senior British official recently acknowledged was one method used by British intelligence in Russia until discovered by Russian security officials. A considerable administrative apparatus stands behind intelligence operatives to develop new technologies, coordinate operations and compile, categorise and analyse the information they gather. Indeed, it could be argued that the greatest weapon for early British intelligence was not the knife or the gun, as might be supposed, but rather the filing cabinet. So although bureaucracy is not the most scintillating focus for a study of intelligence, it was the establishment of a bureaucracy that brought intelligence into the modern era.

Britain emerged from the First World War victorious but in tatters. A postwar recession set in and cuts were made across government, and the intelligence services were no exception. These cuts to MI5’s budget and staff left the service a shadow of its wartime self. Yet the basic features and methods that had existed before Britain entered the Great War continued to underpin intelligence operations. The organisation of British counter-intelligence was actually developed in the years immediately preceding the war with the founding of the Secret Service Bureau (SSB). Its core components were a Preventive Branch (security) and a Detective Branch (investigations). Effectively ‘distinct but inseparable members of a single organism’, they were joined by the Administrative Branch, which was carved off from the Preventative Branch soon after the war began. Together, these comprised the tripartite soul of Britain’s counter-espionage apparatus.

Many years later, one practitioner observed that ‘counterintelligence consists of two matching halves, security and counterespionage’. Security ‘consists basically of establishing passive or static defences against all hostile and concealed acts, regardless of who carries them out’.