Nigel de Grey

De Grey joined the Royal Naval Volunteer Reserve and served in Belgium. In early 1915 he was transferred to Naval Intelligence Division, Room 40 codebreaking section. He, Dilly Knox and Reverend William Montgomery decrypted the Zimmermann Telegram on 17 January 1917. The Zimmermann Telegram was from the German foreign secretary Arthur Zimmermann to the German ambassador Heinrich von Eckardt in Mexico, telling him to offer the Mexican government the return of the states of Arizona, Texas and New Mexico as an inducement to Mexico to side with Germany against the United States. The public disclosure of this secret Mexican-German pact brought the US into World War I. De Grey was promoted and assigned to run the NID's Mediterranean section, liaise with the director of Italian naval intelligence and focus on Austrian cipher traffic.

In World War II Nigel de Grey was assigned to the "Government Code and Cypher School" (GC&CS) at Bletchley Park, where he concentrated on German traffic encrypted on the Enigma cipher machine. In September 1941 he provided a report to the Prime Minister with the first references from German authorities to their own police battalions systematically levelling villages and removing their populations. One signal boasted of 30,000 executions "in the central area". Following a warning made in a speech to parliament by Churchill, a German circular in October 1941 cautioned that no further references to "sensitive operations" should be made on wireless channels.

After World War II de Grey remained with GC&CS, which became GCHQ in 1946. Eventually he became a deputy director and led a team working on Soviet cable traffic. He retired in 1951 and died a very short time later of a heart-attack in Oxford Street, London. His wife, whom he married in 1910, survived him.

• Nigel West, "Grey, Nigel Arthur de (1886-1951)" in the Oxford Dictionary of National Biography
• Paul Gannon, "Inside Room 40: The Codebreakers of World War I", London, 2010