Polish-French-British meeting at Paris in January 1939. The Poles were under order to disclose nothing of importance at this time, leaving the British codebreakers disappointed. However Knox's description of his system of rodding impressed the Polish codebreakers, and they requested his presence at a second meeting. Knox attended the second Polish-French-British conference, held on 25–26 July 1939 at the Polish Cipher Bureau facility (at Pyry, south of Warsaw, Poland). Here, the Poles began to disclose to their French and British allies their achievements in solving Enigma decryption. Although Marian Rejewski, the Polish cryptographer and mathematician who solved the plugboard-equipped Enigma used by Nazi Germany, approached the problem through permutation theory (whereas Knox applied linguistics), a good personal relationship was quickly established at the conference. The good impression made by Rejewski on Knox played an important role in increasing recruitment of mathematicians to Bletchley Park. Knox was chagrined — but grateful — to learn how simple was the solution of the Enigma's entry ring (standard alphabetical order). After the meeting, he sent the Polish cryptologists a very gracious note in Polish, on official British government stationery, thanking them for their assistance and sending "sincere thanks for your cooperation and patience". Enclosed were a beautiful scarf featuring a picture of a Derby winner and a set of paper 'batons'. These 'batons' were known as rods to the British and had been used to solve the Spanish Enigma. Knox's rodding method was later used to break the Italian Naval Enigma. Turing's bombe Alan Turing worked on Enigma during the months leading to the outbreak of the Second World War in September 1939, and occasionally visited GC&CS's London HQ to discuss this problem with Knox. In the 1939 register Turing was recorded in Naphill, staying with Knox and his wife. By November 1939 Turing had completed the design of the bombe — a radical improvement of the Polish bomba. Second World War Knox's rodding method To break non-steckered Enigma machines (those without a plugboard), Knox (building on earlier research by Hugh Foss) developed a system known as 'rodding', a linguistic as opposed to mathematical way of breaking codes. This technique worked on the Enigma used by the Italian Navy and the German Abwehr. Knox worked in 'the Cottage', next door to the Bletchley Park mansion, as head of a research section, which contributed significantly to cryptanalysis of the Enigma. Knox's team at The Cottage