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Heroes of British Signals Intelligence

British Signals Intelligence (Sigint) has involved thousands of 'heroes' over the years - people with unique skills and extraordinary ingenuity who have made a huge difference to the defence of this nation. Just a few of them are described here.

Nigel de Grey

In 1917, Nigel de Grey, a young Naval Lieutenant and code breaker in the Admiralty's Room 40, played the key role in 'breaking-out' the "Zimmermann Telegram". This was sent by the German Foreign secretary Zimmermann to his Ambassador in Mexico, announcing Germany's intention to open hostilities against the USA. Britain's disclosure of the contents of the telegram to the US government was instrumental in their decision to enter World War 1.

Nigel was assigned to the Government Code and Cypher School (GC&CS), Bletchley Park, at the outbreak of WW2, and was ultimately responsible for liaison with very senior customers, including Winston Churchill.

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Commander Alastair Graham Denniston

A leading code breaker in Room 40 at the Admiralty, during World War 1, Alastair Denniston was the first head of GC&CS in 1919. He led the organisation during the inter-War years, oversaw the move from London to Bletchley Park and led work to establish closer liaison with US Sigint experts.

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James Ellis

James Ellis, a mathematician and computer scientist, joined GCHQ (then at Eastcote, West London) in 1952, having previously worked for the Admiralty. James worked on a number of important cryptographic developments but his identification of the concept of Public Key Cryptography (PKC) was the most significant and far-reaching.

This discovery remained classified for a long time and was, at first, only made available for official governmental communications. However, PKC was also discovered and developed commercially, and is now the basis for all secure transactions on the Internet.

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Thomas 'Tommy' Flowers

Tommy Flowers, an employee of the General Post Office's Research Section was appointed by GC&CS in 1943 to lead the team that designed and constructed COLOSSUS, the first large-scale electronic machine and the forerunner of the modern computer. Colossus was used against the German enciphered teleprinter system 'Fish', and had a processing speed of 5000 characters per second. Eventually ten COLOSSI were built, but only one survived the war.

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Alfred Dillwyn 'Dilly' Knox

A Greek scholar, 'Dilly' Knox was one of the original members of the Admiralty's "Room 40" Sigint cell in the First World War, and became Chief Assistant at GC&CS in 1940. He is credited as the code breaker who achieved the first GC&CS successes against Enigma.

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Brigadier John Hessell Tiltman

Generally acknowledged as the greatest British code breaker of all time, John Tiltman was first attached to GC&CS in 1920. He founded the Military Section in 1930 and remained its Head throughout the World War II. Between the wars, he was responsible for breaking many codes and cyphers, particularly those used by the Comintern (the Moscow-controlled international network of Communist parties).

One of his greatest achievements was breaking the main Japanese naval code, JN25, shortly after it was introduced in June 1939. And in 1941 he deciphered the message which led to the solution of the German High Command's teleprinter system 'Tunny'.

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Alan Mathison Turing

Posthumously, the most famous member of GC&CS, Alan Turing joined Bletchley Park in 1939. He invented the basis of cryptanalytic mathematics and special-purpose analytic machines, making major contributions to the exploitation of Enigma and other German cipher systems.

Turing also played a key role in developing Colossus, the world's first programmable computer. After the war, working at Manchester University, he and Max Newman led a team that produced Britain's first general purpose stored programme computer (the Ferranti Mk 1).

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William Gordon Welchman

Gordon Welchman, who joined GC&CS in 1939, helped to break the Enigma code. His 'diagonal board' revolutionised the effectiveness of Alan Turing's special purpose machines (Bombes) which were used to tackle Enigma.

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