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: SHARK, that U-boat cipher keys for April 12 have been broken; on North Africa: a German Air Force (GAF) report on the ground situation as of April 12-13; of the GAF's intentions for April 15; that GAF Tunis is concerned to provide adequate air defences for occupied airfields, on April 14; and that the GAF are to attack harbours on April 15; on the Mediterranean: that the Air Officer Commanding (AOC) is to arrive in Sardinia for the operations of arriving bomber units on April 15; of orders for support of the operation, on April 14; of Ju88s flying to Villacidro with armour-piercing bombs, on April 14; of the transfer of a GAF Stuka unit to Sardinia, on April 14; on fighter protection for GAF bombers for attacks on harbours, on April 14; and of a heavy Allied bombing raid on GAF Elmas' airfield, on April 14; on the Southern Russian Front: of Soviet penetration in Kuban by 2-3 divisions, on April 14; and that the GAF are to support a counter attack against the above penetration on April 15.