Why is the bottom button of a man’s waistcoat always left undone?
As Edward the 7th progressed in years, so did his girth! To accommodate this, he began to leave the bottom button of his waistcoat undone. He thought that it looked elegant and those men –eager to win favour from the king’ followed “suit”.
Taken from: Now You Know: Royalty, (Lennox, 2009)