Experts: Unbreakable code message found on WWII carrier pigeon Royal Pigeon Racing Association, courtesy Bletchley Park Trust This coded message from World War II was found in a canister still attached to the leg of a dead carrier pigeon. LONDON - A coded message from World War II found on the leg of a dead carrier pigeon in an English chimney cannot be deciphered, according to British intelligence agents. The handwritten message on a small sheet of paper headed "Pigeon Service" was found earlier this month in a small red canister still attached to the pigeon's leg, the GCHQ agency said in a statement posted on its website. The pigeon is thought to have been one of the 250,000 used by British forces - including secret agents working behind enemy lines in German-occupied Europe - during the 1939-1945 war. The message was signed and appears to say "Sjt W Stot," GCHQ said, adding that nothing is known of this individual or their unit. Sjt is an abbreviation of the old-fashioned "serjeant" spelling of the army rank. 'Tribute' to code-makers It was destined for a place code-named "X02," but it is also not known what this means. It contains 27 five-letter code groups, but GCHQ said it was impossible to decipher the message without the relevant code book. "During the war, the methods used to encode messages naturally needed to be as secure as possible and various methods were used," the agency's statement said. The senders would often have specialist code books in which each code group of four or five letters had a meaning relevant to a specific operation, allowing much information to be sent in a short message. For added security, the code groups could then themselves be encrypted," it said. "Although it is disappointing that we cannot yet read the message brought back by a brave carrier pigeon, it is a tribute to the skills of the wartime code-makers that, despite working under severe pressure, they devised a code that was undecipherable both then and now," it added. Courtesy Bletchley Park Trust It is thought a "one-time pad" may have been used to encrypt the message. The advantage of this system is that, if used correctly, it is unbreakable as long as the key is kept secret. The disadvantage is that both the sending and receiving parties need to have access to the same key, which usually means producing and sharing a large keypad in advance," GCHQ said. The pigeons carried a wide variety of messages, "flying the gauntlet of enemy hawk patrols and soldiers taking potshots at them to bring vital information back to Britain from mainland Europe," GCHQ added. Each had its own identity number and the Bletchingley message contains two such numbers - NURP.40.TW.194 and NURP.37.OK.76. Either could be the dead pigeon's number.