Rejewski had written a "Report of Cryptologic Work on the German Enigma Machine Cipher" in 1942. Before his 1967 retirement, he began writing his "Memoirs of My Work in the Cipher Bureau of Section II of the General Staff", which were purchased by the Polish Military Historical Institute, in Warsaw. Rejewski had often wondered what use Alan Turing (who in early 1940 had visited the Polish cryptologists at "PC Bruno" outside Paris) and the British at Bletchley Park had ultimately made of the Polish discoveries and inventions. For nearly three decades after the war, little was publicly known due to a ban imposed in 1945 by British Prime Minister Winston Churchill. In a 1967 book Władysław Kozaczuk, associated with the Military Historical Institute, disclosed Poland's breaking of the German Enigma ciphers.