Prince Philip's 90th birthday celebration on Sunday was a special celebratory service attended by a total of 750 close friends and family. Joining the royal celebrations at Windsor Castle's St George's Chapel were the newly-weds, Prince William and Kate.

Kate looked stunning as she strolled down the walkway in a blue brocade frock coat and nude LK Bennett heels. However, it was her coat that caught the eyes of the onlookers. The 29-year old wore the same coat in 2009 for the marriage of close friend, Nicolas van Cutsem and Alice Hadden-Paton.

Nevertheless, the Duchess has infused new life into the periwinkle blue Jacquard coat dress by teaming it with a blue hat and nude heels. It seems that Kate has decided to join the royal tradition of recycling favorite garments; a policy often followed Queen Elizabeth herself and the Princess Royal. In fact, the black and white cocktail dress that she wore to the wedding of close friend Sam Waley-Cohen was the same dress that she wore in 2007 while she was with Pippa.

Among the guests invited for the occasion were members of the royal family including Prince Charles, Duchess of Cornwall, Prince Harry, Princess Beatrice and Eugenie, Earl and Countess of Wessex, the Princess Royal and her husband Vice Admiral Timothy Laurence, daughter Zara Phillips and son Peter Phillips and his wife Autumn.

Check out the latest pictures of stunning Kate below.