As you might have guessed by its name, this tiara was made by Cartier and is actually a more recent addition to the royal jewel collection. Queen Elizabeth's father bought it for his wife only weeks before they became king and queen in 1936. It was gifted to Elizabeth on her 18th birthday, then lent around the royal family, including to Princess Margaret and Princess Anne. Most recently, it was the wedding tiara chosen by Kate Middleton at her 2011 wedding. Papas estimates the worth of this tiara to be between £750,000 and £1.25 million.