At 4'10", Jean Valentine was big enough to leave her parent's home in Scotland during the Second World War but she wasn't exactly what British officials had in mind to help them crack encrypted messages from the Germans.

After her naval training, the 18-year-old met with officers to learn what her assignment would be. Instead, one of the men told her to "stand up and sit down."

The officers were looking for women at least 5'4" or taller to operate the Turing Bombe, a machine more than 6" in height that was used to crack encrypted radio transmissions from the Nazis.

For Valentine, who had cited a love for cryptic crossword puzzles on her Navy application, they made an exception.

She was sent to London to work as a code breaker.

"They produced a little wooden plank a couple of inches high, I stood on that and then I was taught to use a Bombe," Valentine, now 84, told CTV.ca in a recent interview from her home in Buckinghamshire.

The Bombe, invented by mathematician Alan Turing, was able to crack German messages created by the Enigma machines the Nazis were using.

Last week, after 14 years in the making, a rebuilt Bombe was unveiled to the public at Bletchley Park, about 64 kilometres northwest of London.

During the war, the machines were set up at Bletchley Park and at various outstations.

Sworn to secrecy, Valentine was one of many women who helped crack thousands of cryptic messages sent over the air by the Germans.

"We had 200 machines all working 24 hours a day," Valentine said.

Even though they'd crack the codes, their supervisors weren't allowed to tell them what the messages were.

"Secrecy and security was of the utmost," Valentine said. "That place stayed secret for many, many years because those of us who worked there were told 'Don't talk' so we didn't," she said.

"Things have changed you know, there's no discipline about nowadays. If we were told not to talk we didn't talk."

The only way the women knew if they'd found something of importance was when a supervisor would tell them "Job Up."

At times, long after a code had been cracked, the women would sometimes learn how their work had helped the mission.

"There's no doubt that it shortened the war by a couple of years because it enabled us to find out where various Germans were going to be and stop them from doing what they wanted," Ruth Bourne, another code breaker, told CTV.ca from her home outside London.

Valentine recounted the time she learned that one of the code breakers had cracked a message indicating the famous German battleship, the Bismarck, was in the fjords of Scandinavia.

To avoid suspicion, five naval flyers were sent out on a routine square search of the North Sea.

"One of them, unknown to him, had the exact map reference of where the Bismarck was at that point," Valentine said.

After spotting the ship, the pilot radioed back to headquarters that he had found the Bismarck.

"We were not compromised because the Germans thought that our spotter plane had seen their ship, not that we had broken in to their encryptions," she said.

After the war, all 210 original Bombe machines were destroyed and the women kept their secret quiet for decades.

Bourne, 83, was one of the women who worked to dismantle the machines so that nobody would know they existed.

It wasn't until the 1970s that the secrecy ban was lifted and the women were allowed to talk about their war-time activities.

Valentine said even her husband didn't know what she had done during the war.

"I didn't tell him about it until it came out into the open air."