The wedding of Prince Charles and Princess Diana (opens in new tab) was exactly 40 years ago today. One such fun fact: Diana had a secret message painted on the soles of her wedding shoes for the big day.

According to The Sun (opens in new tab), Diana's wedding shoes were "a beautiful suede heel with 542 sequins and 132 pearls in a sweet heart-shaped pattern." Diana requested one last detail be added to the already impressive shoes, and had a small "C" and "D" painted on the bottom of the shoe as a secret message just for her and Charles on their special day.

According to shoemaker Clive Shilton, who spent six months on these stunning heels, the secret message was not the only thing Diana requested about the shoes on her wedding day. She was also very concerned about her height in heels (opens in new tab).

"(Diana) was a very shy, sweet, smiling young girl," Shilton told the Daily Mail. 'Her main concern was not to look taller than Prince Charles.'

Later, as the shoes were displayed, a secret message was revealed. Even with the soles turned up, the "message" is still quite hidden. If you look very (very, very) closely, you can see the letters "C" and "D" on the floral sole, just above the straight edge of the heel. If she had tripped, you would have seen much more