(Conel) Hugh O'Donel Alexander (19 April 1909–15 February 1974) was a British cryptanalyst and chess player. He worked on the German Enigma machine at Bletchley Park during World War II, and was later the head of the cryptanalysis division at GCHQ for over 20 years.

Contents 1 Codebreaking at Bletchley Park 2 Career at GCHQ 3 References 4 External links

Codebreaking at Bletchley Park

In February 1940 Alexander arrived at Bletchley Park, the British codebreaking centre during World War II. He joined Hut 6, the section tasked with breaking German Army and Air Force Enigma messages. In 1941, he transferred to Hut 8, the corresponding hut working on Naval Enigma. He became deputy head of Hut 8 under Alan Turing. Alexander was more involved with the day-to-day operations of the hut than Turing, and, while Turing was visiting the United States, Alexander formally became the head of Hut 8 around November 1942.

In October 1944, Alexander was transferred to work on the Japanese JN-25 code.

Career at GCHQ

In mid-1946, Alexander joined GCHQ, which was the post-war successor organisation to the Government Code and Cypher School (GCCS) at Bletchley Park. By 1949, he had been promoted to the head of Section H (cryptanalysis), a post he retained until his retirement in 1971.

References

• H Golombek and W R Hartson, The best games of C H O'D Alexander (1976).
• Stuart Milner-Barry, A Tribute to Hugh Alexander in H Golombek and W R Hartson, The best games of C H O'D Alexander (1976), 1-9 [1](PDF).
• Biography by Harry Golombek, revised by Ralph Erskine, in Dictionary of National Biography (Oxford, 2004).

External links