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 report on the Russian Front: a detailed summary of German intentions on the Central Front in relation to a forthcoming Axis major attack, Operation CITADEL, on April 25; and correspondence on procedures for the Chief of the Imperial General Staff (CIGS) to pass on information to the Soviets on Operation CITADEL.