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 message: to the Assistant Chief of Air Staff Intelligence (ACASI) for the Chief of the Air Staff (CAS) from C, including a note from the Prime Minister (PM) and a response from the CAS to a German report of a Panzer group attack which took the British by surprise and without air support, on January 21.