Prince William and Kate Middleton's engagement has only just been announced, and yet the nation is already gripped in royal wedding fever as more details emerge. Speculation over Kate Middleton's engagement diamond have been put to rest, as Clarence House have confirmed that Prince William gave his mother's engagement ring to Kate when she accepted his proposal of marriage. The stunning engagement ring is an 18-carat blue sapphire stone surrounded by smaller diamonds and belonged to the late Princess of Wales. Speaking about his decision to give Princess Diana's engagement ring to his new bride-to-be, William explained that he wanted his late mother to be part of the royal wedding. A truly lovely gesture. The pair made their first official public appearance as an engaged couple at photocall at St James Palace (pictured above).