PoW's secret codes that fooled the Nazis: How Spitfire pilot held in 'Great Escape' camp sent coded message to British MI9 spies hidden in letter about 'glorious weather' to his mother
The coded message was sent by Peter Gardner in a letter that was addressed to his mother and which accompanied a photo of an 'old school friend'. Above: The tiny coded message with the photo.
Source: dailymail.co.uk