Conel Hugh O'Donel Alexander

Conel Hugh O'Donel Alexander, known as Hugh Alexander and C. H. O'D. Alexander, was an Irish-born British cryptanalyst, chess player, and chess writer. He worked on the German Enigma machine at Bletchley Park during the Second World War, and was later the head of the cryptanalysis division at GCHQ for 25 years. He was twice British chess champion and earned the title of International Master.