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 contains a message from C to the First Sea Lord (ISL); a comment from the Prime Minister (PM); and a note from the First Sea Lord (1SL) on a report of the sailing of a large convoy from Italy protected by heavy Italian naval forces, possibly sailing on January 23.