Government Code and Cypher School: Signals Intelligence Passed to the Prime Minister, Messages and Correspondence

A file of signals intelligence reports, messages, and correspondence issued by the Government Code and Cypher School and sent by the head ('C') of the Secret Intelligence Service (MI6) to the Prime Minister, Winston Churchill. This file includes the following correspondence: a request from C to the First Sea Lord (ISL) for comments on the attached message and response concerning the transfer of German bomber units to northern Norway for operations against the Royal Navy.