All the good knights were leaving for the Crusades.
One knight told his best friend - "My bride is without doubt one of the most beautiful women in the world. It would be a terrible waste if no man could have her. Therefore, as my best and most trusted friend, I am leaving you the key to her chastity belt to use should I not return from the Crusade."
The company of knights were only a mile or so out of town when they noticed a cloud of dust approaching.
Thinking it might be an important message from the town the column halted.
A horseman approached. It was the knight's best friend.
He yelss - "Hey, you gave me the wrong key!!"