(CBS News) Prince William was made a Knight of the Order of the Thistle - the highest honor available in Scotland - in a ceremony in Edinburgh on Thursday.
William, 30, and wife Kate (who are known in Scotland as the Earl and Countess of Strathearn) were joined by other members of the royal family for the event, which took place at St. Giles Cathedral.
The BBC reports that during the short ceremony, Queen Elizabeth II said to her grandson, "It is our pleasure that his Royal Highness the Prince William, Earl of Strathearn, be installed a Knight of the most ancient and most noble Order of the Thistle."
The prince then moved to a vacant stall within the cathedral's Thistle chapel before taking an oath, in which he promised to be "loyal and true to my Sovereign Lady the Queen, and the members of this Order."
"I shall maintain the honor and dignity of the most ancient and most noble Order of the Thistle to the best power if God let," he said, according to the BBC. "I shall never bear treason about in my heart against our Sovereign Lady the Queen, but shall discover the same to her. So defend me God."
Appointments to the Order of the Thistle can only be made by the queen. She is a member, as well as Prince Philip, Duke of Edinburgh, Prince Charles and Princess Anne.
Kate, 30, wore a primrose-colored coat dress by Emilia Wickstead for the event, according to the Daily Mail, along with a hat by British milliner Whiteley that she has worn numerous times before.
She also carried a folded scarf with a Strathearn tartan print, the Mail notes, in a nod to her Scottish title.
Thousands reportedly gathered on the Royal Mile to catch a glimpse of the royal family as they made their way into the cathedral for the Thursday morning ceremony.
The 45-minute service, which was followed by a special parade featuring 400 pipers, was part of the queen's Diamond Jubilee celebrations in Scotland marking her 60 years on the throne.