Cracking Codes and Changing History: The Secret World of Bletchley Park

During World War II, as battles were waged on land and at sea, nearly 10,000 Britons, working in wooden huts on the grounds of a sprawling English estate called Bletchley Park, fought another battle.

These heroes included Dilly Knox, who relaxed by translating ancient Greek scrolls, mathematicians, linguists – and about 7,500 ordinary women from all walks of life. This motley crew worked around the clock to crack Nazi codes and helped shorten the duration of the war by at least two years, saving thousands of Allied lives in the process.

Code-named Station X, Bletchley Park was a Victorian estate situated on 53 acres of grounds fifty miles north of London. In 1938, fearing that war with Germany was imminent, the British government began to secretly recruit cryptographers, linguists, and other talented people to work there. If there was a war, these citizens would be tasked with intercepting and deciphering enemy codes. These codes, encrypted messages that the Germans sent to one another over radio waves, contained detailed accounts of Nazi troop movements, bombing targets and strategic plans. Failure to crack the Enigma code, which changed daily, could result in the death of thousands of soldiers and civilians.

When World War II began in 1939, there were only about 200 people working at Bletchley Park, but the government quickly began enlisting more. Some of them were chosen for their special skills, but many were ordinary young women, some as young as seventeen.

One woman who was recruited to work at Bletchley Park was Mavis Lever, a teenage student at the prestigious Cambridge University. She came from an ordinary, middle-class household, and her family initially thought the Nazi party might be a force for good “because it seemed like they were bringing a country that was on its knees back to the modern world,” Mike Chapman, my knowledgeable Bletchley Park tour guide explained.

Mavis enrolled at Cambridge to study German, but “as it became apparent what the Nazis were really about, she was so disgusted that she dropped out of university,” Chapman continued. Based on her academic abilities, and German language skills, she was then recommended to Dilly Knox.

Alfred “Dilly” Knox had been a leading codebreaker during World War I. At Bletchley Park, he led a team of women, known as “Dilly’s Girls,” in breaking the German “Enigma code,” which was initially thought to be unbreakable. Mavis quickly became a critical member of Dilly’s crew.

Mathematician Maragret Rock was another successful codebreaker. She joined Dilly’s team in 1940 and impressed him so much that he said, “Miss Rock…is actually 4th or 5th best of the whole Enigma staff and quite as useful as some of the 'professors'. I recommend that she should be put on the highest possible salary for anyone of her seniority.’”

On my tour, Mr. Chapman emphasized just how highly Dilly esteemed these women by sharing this quote of his: ‘Give me a Rock and a Lever [Mavis’ and Margaret’s last names] and I can break anything.’”

THE ENIGMA GIRLS

Of course, not all the women who worked at Bletchley Park were mathematical geniuses like Mavis and Margaret. All of them, however, had to sign the Official Secrets Act, which meant they were “unable to disclose the slightest information about [Bletchley Park],” writes Candace Fleming in The Enigma Girls, a book all about the Bletchley Park women. If they did so, they would be committing treason, which meant they could be executed for betraying their country. 

Jane Hughes, just eighteen years old when she was recruited, told her parents she was doing clerical work at Bletchley Park. For over thirty years, she and her fellow female codebreakers did not breathe a word to their parents or friends and later their husbands, children or grandchildren about the true nature of their wartime work.

Jane became a world-famous opera singer, Mavis continued her cipher work and others married and raised families without anyone ever knowing about their crucial contribution to the war effort.

In 1977, however, the British government “released 70,000 intelligence documents related to the work done at the park” and suddenly the women broke their collective silence – some wrote books and magazine articles about their experiences, while others gave interviews and appeared in TV documentaries.

 “Working at Bletchley Park was the most important thing any of us have ever done in our lives,” Jane once remarked in an interview. “We just didn’t realize it at the time.”