John R.F. Jeffreys facts for kids

A demonstration of Zygalski sheets, a tool for breaking the Enigma machine. This Polish invention was shared with the British in 1939, and the enormous task of manufacturing two complete sets of the sheets was supervised by Jeffreys.

John Robert Fisher Jeffreys (born January 25, 1916 – died January 13, 1944) was a brilliant British mathematician. During World War II, he became a secret codebreaker. He played a very important role at Bletchley Park, helping to crack the German Enigma machine codes.

John Jeffreys: A Codebreaking Hero

John Jeffreys was a smart research fellow at Downing College, Cambridge. In September 1939, he joined the top-secret codebreaking team at Bletchley Park. He worked alongside other clever mathematicians from Cambridge, like Gordon Welchman and Alan Turing. These three, along with Peter Twinn, worked under Dilly Knox. Their special job was to figure out the German Enigma machine. They started their important work in a small building called "The Cottage" at Bletchley Park.

Cracking the Enigma Code

John Jeffreys was put in charge of making special paper sheets. These sheets had holes punched in them and were used to help break the Enigma codes. This big task took him over three months to finish. One type of these sheets was called Zygalski sheets. Polish codebreakers had shared this clever method with the British. Another type was called "Jeffreys sheets." These were different and helped show how the Enigma machine's parts worked together. Polish codebreakers used Jeffreys's sheets in France to break the first wartime Enigma message in January 1940.

Leading Hut 6

In early 1940, a new section was created at Bletchley Park. It was called "Hut 6" because it was first located in that building. This team's job was to solve German Army and Air Force Enigma messages. John Jeffreys was chosen to lead Hut 6 along with Gordon Welchman. Jeffreys was in charge of the "Sheet-Stacking and Machine Room activities." This meant he managed the use of the special punched sheets and the machines that helped with codebreaking. Welchman handled other important tasks like keeping records and working with intelligence teams.

A Tragic Loss

In May 1940, John Jeffreys took a break. Sadly, he became very ill and was diagnosed with tuberculosis and diabetes. He passed away in January 1944. Gordon Welchman, his colleague, later remembered how much everyone at Bletchley Park liked Jeffreys. His death was a very sad loss for all of them. People felt great sympathy for his fiancée, Pat Hempsted. She had been a part of his team from the very beginning. She helped punch the sheets and test the results that led to their early code breaks.