Kate at 40: How the Duchess of Cambridge's style evolved from youthful sparkle to timeless elegance

Since joining the royal family in 2011, Catherine, Duchess of Cambridge -- known by many as Kate -- has rarely faltered on her unwritten obligation to appear manicured and immaculately dressed in the public eye. And while the duchess is renowned for her preppy tweeds and tailored blazers, she earned her true fashion credentials through a sharp eye for occasion wear.