The following report is taken from the Special Operations Executive Signals history. It details the use of 'finger printing' Morse W/T operators in order to accurately identify the individual by their signals signature using statistical methods.
The following document was written by the British Director of Naval Intelligence in April 1941. It shows the conflicting priorities between the collection of intelligence on the one hand and the organisation of sabotage and subversion on the other. From the point of view of the Naval Intelligence Department (NID), the intelligence gathering abilities of the Secret Intelligence Service, or MI6 as they are more commonly and incorrectly known as, was of more importance than the subversive activities of the Special Operations Executive (SOE) in wartime Europe. The strained early relationship between SIS and SOE is well known but it is interesting to see it spelt out so directly by the DNI in this document.