SCOTT SIMON, HOST:
At first it reads like any other letter home. My dear mommy and daddy, it begins. Last week I received a short letter from Robert. It was written 64 years ago by John Pryor, who was a British prisoner of war in a German camp, but the letter is not ordinary.
John Pryor put a secret code into his descriptions of everyday life in a prison camp to try to tip British Intelligence about what he could observe even in captivity. A team of researchers at Plymouth University has just helped John Pryor's son decode his father's wartime letters home. Stephen Pryor joins us now from BBC studios in Plymouth. Thanks very much for being with us.
STEPHEN PRYOR: Thank you.
SIMON: What kind of information was your father trying to get out?
PRYOR: There were two types of information buried in these letters. There is military intelligence going back about munitions dumps, about submarines that have been sunk and information requests for British Military Intelligence in London to send maps and German currency and German I.D. to help them with their escape plans.
SIMON: How did he manage that?
PRYOR: Well, it's a complicated code. Can I give you an example...
PRYOR: ...of a sentence?
PRYOR: This one letter is about the sinking of a submarine called HMS Undine and there's a sentence here that says: I am pleased that I have got the two letters telling me of my cousin's latest event. How happy he must undoubtedly be. That sentence is a spelling of the name of the submarine, HMS Undine.
SIMON: What is it, the first letter of every word?
PRYOR: More than that. You take the first letter of every word in groups of three and then it goes into a three-dimensional matrix which you have to remember in order to decode and get the sequence of letters to produce the name of the vessel.
SIMON: Did the recipients of these letters know what he was doing?
PRYOR: Military intelligence, once they knew that a prisoner had the code and would be writing home, informed the relatives that some letters may read a little strangely, so the relatives would have known that the letter was in code, but they would never have been told what was in the letters.
SIMON: Mr. Pryor, even given what we understand now, the very good reason for some of the stilted language and innocuous observations, what do you learn about your father by rereading these letters?
PRYOR: My father, until the later years of his life, didn't talk much about his war experiences, but I can see now that he was among tens of thousands of other young men who gave up their youth in captivity. He and his peers took incredible risks and that has only made me admire him and all the other men for their resilience and ingenuity.
SIMON: Stephen Pryor, who worked with Plymouth University researchers to crack the code in his father's letters home from a POW camp in Germany. Mr. Pryor, thanks so much.
PRYOR: It was a pleasure.
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SIMON: This is NPR News.
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