Dilly Knox

Alfred Dillwyn 'Dilly' Knox (23 July 188427 February 1943) was a British codebreaker and classical scholar at King's College, Cambridge. He was a member of the World War I Room 40 codebreaking unit, and later at Bletchley Park he worked on the cryptanalysis of the Enigma machine until his death in 1943.

Family and education

Dillwyn Knox, the fourth of six children, was the son of Edmund Arbuthnott Knox, and the brother of Ronald Knox, E. V. Knox and Wilfred. L. Knox. He was father of Oliver Arbuthnot Knox.

Dillwyn, known as "Dilly," Knox was educated at Summer Fields School, Oxford, and then Eton College. He studied classics at King's College, Cambridge, and was elected a fellow in 1909.


Knox was one of the British participants in the July 25, 1939, Polish-French-British conference held at the Polish Cipher Bureau facility at Pyry, south of Warsaw, Poland, in which the Poles disclosed to their French and British allies their achievements in Enigma decryption. 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 enclosing a beautiful scarf featuring a picture of a Derby race, and a set of paper batons that he had presumably used in his attempts to break the German Enigma.

To break non-steckered Enigma machines, Knox used a system known as rodding, a linguistic as opposed to mathematical way of breaking codes. This technique was applied successfully against the Enigma used by the Italian Navy and the German Abwehr.

Knox's work was cut short as he fell ill with lymph cancer. When he became unable to travel to Bletchley Park, he continued his cryptographic work from his home in Hughenden, Buckinghamshire, where he received the CMG. He died on 27 February 1943.


  • Penelope Fitzgerald, The Knox Brothers, New York: Coward, McCann, & Geoghegan, 1977; revised edition, Washington, DC: Counterpoint, 2000.
  • David Kahn, Seizing the Enigma, 1991, pp. 25-26, 84-85
  • Mavis Batey, "Marian and Dilly", pp. 67-74 in Marian Rejewski 1905–1980, Living with the Enigma Secret, 2005.
  • Władysław Kozaczuk, Enigma: How the German Machine Cipher Was Broken, and How It Was Read by the Allies in World War Two, edited and translated by Christopher Kasparek, Frederick, MD, University Publications of America, 1984.

External links

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