​Benedict Cumberbatch, Alan Turing and Enigma

The enigma of WWII codebreaker Alan Turing 07:30

Germany's top-secret World War II code was called "Enigma." The Englishman who played a key role in breaking that code was very much an enigma himself. Anthony Mason this morning helps decode the decoder.

In 1939, as Nazi troops were invading Poland and threatening Europe, British intelligence secretly moved its code-breaking operation to a country estate about an hour outside of London.

At Bletchley Park, the British covertly recruited a team of the country's top cryptographers to try to crack the Germans' "Enigma" code.

Among them: a young mathematician named Alan Turing.

In the new film, "The Imitation Game" (out next month), Benedict Cumberbatch plays the mathematics prodigy who would change the course of the Second World War.

Commander Denniston: "How old are you, Mr. Turing?"
Turing: "27."
Denniston: "And how old were you when you became a fellow at Cambridge?"
Turing: "24"
Denniston: "And how old were you when you published this paper that has a title I can barely understand?"
Turing: "Uh, 23."
Denniston: "And you don't think that qualifies you as a certified prodigy?"
Turing: "Well, Newton discovered binomial theorem aged 22. Einstein wrote four papers that changed the world by the age of 26. As far as I can tell, I've barely made par."

Mason asked Cumberbatch, "That must be sort of intimidating, to try to have to put all that on the screen." "Hell, yeah it is," he replied.

To better understand Turing's work, Cumberbatch familiarized himself with the Germans' encryption device, called the Enigma Machine, on display at London's Imperial War Museum.

It was the machine that Turing was warring against. "Exactly," said Cumberbatch. "This is the enemy. The 'crooked hand of death,' as it's called in the film."

"Turing viewed this as a mathematical problem, didn't he?" asked Mason.

Benedict Cumberbatch as Alan Turing in "The Imitation Game." Weinstein Company

"Absolutely. I mean, he really did. But he also understood that to beat a machine, you had to use a machine rather than humans, because there just wasn't enough time."

What was happening at Bletchley Park was absolutely top secret, said archivist Victoria Worpole. "And in fact, everybody who worked here kept the secret for 30 years after the war."

She said the code-breaking operation was headquartered in Hut 8. It's where Turing and his team worked with captured German machines.

The Nazis set their codes on the Enigma's alphabetic keyboard: "And each time you press it, the light lights up and tells you what to write down as your ciphered text," said Worpole.

The code was reset every day, so the cryptographers had only 24 hours to crack it. The odds: One in 159 million million million.

Code analysts working at Bletchley Park. U.K. Government Communications Headquarters

Turing conceived of a massive machine with rotating drums that would mathematically eliminate potential codes.

"You've got a column on three verticals," said engineer Tony Jarvis. "The drums actually replicated one Enigma machine. And so what you've got are actually 36 Enigmas all looking for an answer."

It took nine months for Turing and his team to design and build a prototype.