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 reports on Bulgaria: of heavy air raids on Sofia, on March 29-30; on South-east Europe: a German Air Force (GAF) summary of the situation up to the morning of March 31, including the raid on Sofia; on East Europe: that the German Traffic Directorate East is unable to supply Army Group A owing to the cutting of rail communications with Lvov, on March 28; and Naval Headlines, covering U-boats failing to attack a convoy; and Japanese reactions to a carrier-strike against Palao.