John Herivel

Born in Belfast on the 29th August 1918 he went on to study Mathematics at Sidney Sussex College, Cambridge in 1937 after being awarded the Kitchener Scholarship.

Herivel was a Cambridge undergraduate mathematician recruited by his tutor Gordon Welchmann to work on the Enigma problem. In the days before the Bombe machines, Enigma cryptanalysis was a laborious manual task where the attacker tested for many different machine configurations. Herivel guessed that at the beginning of the day, hurried operators might make choices that provided information about the configuration. In such cases, one could test the likely settings first, and hopefully save a lot of time.

The Herivel tip or 'Herivelismus', was not immediately used. Later, when the Luftwaffe changed their protocols, the indicator method developed by Polish cryptanalysts stopped working. Herivel's insights was now key to breaking the new traffic.

Herivel remained at Bletchley throughout the war, later acting as assistant to Dr Max Newman. Here he helped Newman make the case for the extra resources for the Newmanry's attack on the TUNNY system. After the war, he went on to a distinguished career as a historian of science. He took his Official Secrets Act obligations seriously, not even revealing his wartime work to his father on the latter's deathbed. In 2008 he was able to write an account of his Enigma work, bringing the expert eye of both the cryptanalyst and the historian to this fascinating time. He died in Oxford on the 18th January 2011.