They were present at the invitation of the newly crowned king.
Along with Their Majesties, there were other royals also present at the ceremony, including Monaco’s Prince Albert and Princess Charlene, Spain's King Felipe and Queen Letizia, Japan's Crown Prince Akishino and Crown Princess Kiko, and Sweden's King Carl XVI Gustaf and Crown Princess Victoria.
Some 2,200 guests had been invited to the ceremony.
The Royal Household Bureau has said that Their Majesties will be in the United Kingdom until Sunday and are staying at The Landmark London hotel.