Brit spook central GCHQ can't decipher a coded message found on a pigeon that died trying to deliver the missive during WWII, and may have to turn to the public for help.
The remains of the bird, found by David Martin in his chimney in Surrey, had a secret message attached - 27 handwritten blocks of code.
The pigeon is reckoned to have flown from Nazi-occupied France, possibly during the D-Day invasions, in June of 1944, and codebreakers at the intelligence agency have been trying to figure out what its message says.
But the problem is that the code could be a one-off encryption, which only the sender and the recipient would have had a key for.
"We didn't really hold out any hopes we would be able to read the message because the sort of codes that were constructed to be used during operations were designed only to be able to be read by the senders and the recipients," GCHQ historian Tony, who asked that only his first name be used, told the BBC.
"Unless you get rather more idea than we have of who actually sent this message and who it was sent to, we are not going to find out what the underlying code being used was."
The code could also have been based on a specific codebook put together for one mission that allowed the maximum information about that operation to be sent in the shortest possible message. If the codebook has since been destroyed, that would also make the encryption practically unbreakable.
Since the message is written on an official pad, historians don't think it was sent by a spy - because a spook wouldn't want to carry anything official around in case they were caught. In fact, the theory is that it was an Army units message, since the abbreviation "Sjt W Stot" is in the message and the Army used that old fashioned spelling of Serjeant.
Experts have also discredited the idea that the bird may have been on its way to codebreaking offices at Bletchley Park, as this was a station to decode German and Japanese messages, not somewhere British military were regularly sending communications.
GCHQ has been able to narrow it down a small bit by pigeon identification numbers. Each of the 250,000 or so birds used as messengers during the war were given an ID number, but this message contains two of these numbers and the agency is unsure which one relates to the pigeon found in the chimney.
Some help from the public could give GCHQ the contextual information it needs to help decode the message, such as the identity of Sjt Stot and clues to the identities of the sender and recipient.
"There are still quite a lot of people alive who worked in communications centres during the war and who might have some knowledge about this and it would be very interesting if anyone did have information if they could put it in the pot and we could see if we could get any further with it," Tony said. ®