5 Secret Historical Codes That Have Still Not Been Cracked

5. The Carrier Pigeon Message

Finding a dead pigeon in your chimney is pretty grim, but for one man, it opened up a whole world of wartime secrets and codes. After uncovering such a decayed body in his home in 1982, David Martin found a plastic capsule around its leg and a piece of paper inside. On this paper was a coded message, which this pigeon was clearly tasked with delivering.

The use of carrier pigeons was widespread during the first and second world wars. This one had the alias 40TW194, and plenty of people have speculated (thanks to its proximity to Bletchley Park, an Allied code-breaking centre near Normandy) that it harboured sensitive information about D-Day.

Eventually, the government itself decided to try and crack the code, with experts at Bletchley Park itself doing their best to uncover the hidden message. However, they fell entirely short, as they didn't have the cypher to translate the information and couldn't figure one out.

When the mystery stumps even those who sent the message, you know you'll never get a solid answer.