Mavis Batey dies at 92; renowned code-breaker for Britain in WWII

Fifty miles north of London lies Bletchley Park, a railway town during World War II that had few, if any, sights to recommend it. It was here, to a rundown estate on the other side of the tracks, that 19-year-old Mavis Batey was dispatched in the spring of 1940.

As Hitler’s forces advanced across Europe, encoded messages from Panzer divisions, U-boats and even the German high command were being intercepted and relayed to the men and women at Bletchley Park, whose job was to break the German code and help Britain and its allies outwit the Axis powers.

Batey, a college student studying German linguistics, became one of Bletchley Park’s nimblest decoders. She decrypted a message that led to a stunning British victory over the Italian navy in the Mediterranean. She also was the first to crack the secret messages of the Abwehr, the German intelligence service, a breakthrough that helped ensure the success of the D-day landings.

“She was the last of the great break-in experts…who broke codes or ciphers that no one else had ever broken,” said British historian Michael Smith, who wrote several books on Bletchley Park. “She was a remarkable woman and someone I will never forget, nor will anyone who ever met her.”

Batey, who earned distinction as a garden historian before her World War II exploits were publicly recognized, died of natural causes Nov. 12 at her home in the West Sussex village of Petworth, said Katherine Lynch of the Bletchley Park Trust. She was 92.

She arrived at her wartime assignment knowing nothing about the Enigma, an electromechanical encryption device developed in Germany around 1918.

Though it resembled a typewriter, with 26 alphabetic keys, it was far more complex, with three or four electrically wired rotors capable of producing endless combinations of coded letters. To make deciphering even more of a challenge, there were a number of different models, each with its own confounding way of changing the input and output, so that, for example, MMMMM might come out QVCTW one day and a different nonsensical jumble the next day. According to Batey, one new decoder fled Bletchley after hearing a detailed description of the Enigma’s convoluted innards.

Batey received the barest of introductions.

“Hello, we’re breaking machines. Have you got a pencil?” her boss, legendary cryptographer Alfred Dillyn (“Dilly”) Knox, said when they met. Then he handed her a stack of coded messages that none of the resident geniuses had been able to crack.

One day she was examining a message sent on the Italian navy’s Enigma and noticed that there was not one L in it. Knowing that the machine never encoded a letter as itself, she suspected that she was looking at a test message a lazy operator had made by repeatedly pressing the L key. With this discovery, “Mavis broke the main Italian naval Enigma,” Smith told The Times last week, “and reconstructed its inner workings on the basis of one single message.”

In March 1941 she decoded a far more important dispatch. The Italian navy had transmitted a message that said “Today’s the day minus three,” signaling a major attack in three days. The next intercepted message supplied details of the battle plan, including the number of Italian warships and the time and location of the assault.

“Why they had to say that I can’t imagine,” Batey said of the first dramatic message when she was interviewed by Smith decades later. “It seems rather daft, but they did.”

The information allowed the Royal Navy to hand Italy its worst defeat at sea: In the Battle of Cape Matapan, off the Greek coast, more than 2,000 Italian sailors died and five Italian ships were destroyed.

Batey’s most noteworthy contribution came in late 1941, when she worked with Knox and another colleague, Margaret Rock, to break the ultra-complex Enigma machine used by the Abwehr. Batey decoded a message between Berlin and Belgrade, the capital of modern-day Serbia, that allowed her team to understand the machine’s encryption process. Days later, she broke the code of a second Abwehr machine.

These breakthroughs were crucial to the success of the Double Cross System, a British operation that used captured German spies to feed false information back to Germany. With the invaluable aid provided by Bletchley Park, Britain was able to confirm the success of its massive deception.

The phony intelligence included misleading reports about where the main Allied invasion force would land, pointing at the Pas de Calais rather than Normandy. Hitler subsequently fortified his forces on the Pas de Calais, dooming his chances of repelling the historic D-day assault on June 6, 1944. President Eisenhower later said that the secrets unspooled at Bletchley Park shortened the war by two years.

“There is nothing like seeing a code broken, that is really the absolute tops,” Batey told Smith in his 1998 book “Station X: The Code Breakers of Bletchley Park.”

Those were heady days for the daughter of a postal worker and a seamstress. Born Mavis Lillian Lever in Dulwich, in south London, on May 5, 1921, she was enrolled at University College, London, when she was recruited for the job she thought would make her a spy like Mata Hari.

Instead, she spent the war years in a dank cottage at Bletchley Park, surrounded by brilliant eccentrics like Alan Turing, the Cambridge mathematician who laid the foundation for modern computing with a decryption machine he called the Bombe.

Batey also met her future husband at Bletchley Park. She and Keith Batey, a mathematician in the unit that decoded German army and air force Enigma messages, married in 1942.

Keith Batey died in 2010. She is survived by their son and two daughters.

In the late 1960s, when her husband became the chief financial officer of Oxford University, Batey took on the restoration of some overgrown gardens near their university-owned home. She became one of England’s best-known garden historians and a leading preservationist, for which she was honored with the title of Member of the Order of the British Empire, or MBE, in 1987.

She was a model for the code-breaker played by actress Kate Winslet in “Enigma,” the 2001 movie about Bletchley Park. Batey told an interviewer that she admired Winslet’s acting, “though perhaps she slightly overdid the dowdiness.”

By then, Batey was regarded as a national heroine, but she was discomfited by such praise.

“I was just part of a team. We were all part of a team. The heroes,” she told London’s Daily Telegraph last year, “were the chaps who were fighting on D-day.”

elaine.woo@latimes.com