A pigeon that's been dead since World War II has created fresh intrigue for British code breakers, who say they're stymied by the code found attached to the bird's leg.
The small corpse, which was discovered at the end of October, was carrying a coded message contained in a red canister, attached to its leg.
UK code breakers have attempted to decipher the message but have found it extremely challenging, reported the BBC, as it's likely it was a one-time only code, not designed to be used again.
"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," said historian Tony of the UK Government Communications Headquarters to the BBC.
Read more from GlobalPost: Indian WWII "spy princess" is honored with a London monument
He added: "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 intelligence agency has concluded that the code can't be cracked without "access to the original cryptographic material," according to GCHQ.
But not all hope is lost: GCHQ is hoping that outside sources can help crack the code—so aspirant code breakers and those harboring WWII era spy notebooks may want to contact the intelligence agency sooner, rather than later.
Read more from GlobalPost: Pigeons brains have 'GPS neurons' to help them navigate, scientists find
Carrier pigeons were widely used during WWII, an elegantly simple solution to the communication problems faced by spies and other covert agents. According to Pigeoncenter.org, the birds were used widely on both sides of the conflict, and were especially useful when troops needed to maintain radio silence.
A 1999 BBC report states that British MI5 agents were deeply concerned by the prospect of Nazi pigeons, as SS chief Heinrich Himmler was especially fond of the birds, and was thought to be using them as part of war-time plans to invade Britain.