UK royals mark Garter Day.

UK royals mark Garter Day. Garter Day is a symbolic occasion June 13, 2011. Britain's royal family has turned out for the annual Order of the Garter service at Windsor Castle.

Queen Elizabeth II was joined by her husband, Prince Philip, the newly-married Duke and Duchess of Cambridge and a host of other royals for the Garter Day ceremony.

Garter Day is a symbolic occasion when holders of the honor, chosen because they have held public office, contributed to national life or served the sovereign personally, meet to celebrate the most senior British order of chivalry.

The former Kate Middleton, also known as the Duchess of Cambridge, grinned broadly as she watched her husband, Prince William, take part in a procession ahead of the service — causing him to blush.

When it comes to fashion, elegance and grace, Britain's royal favorite and Duchess of Cambridge Kate Middleton never fails to impress her admirers.

At the recent 'Order of the Garter' service at Windsor Castle on Monday, the 29-year old looked stunning in a mid-sized Philip Treacy headpiece perched in a slating manner on her open hair along with natural make-up; a look often referred to as the Duchess' "signature style."

Her light blue-grey dress was complimented with a matching coat, giving her a regal and elegant look. Over 6,000 people were present to watch the pageantry of the Order of the Garter service. Founded in 1348, the Order of the Garter is the most senior and the oldest British Order of Chivalry. The Order, consisting of the King and twenty-five knights, honors those who have held public office, who have contributed in a particular way to national life or who have served the Sovereign personally.

At the service, every knight is required to display a banner of his arms in the Chapel, together with a helmet, crest and sword and an enamelled stallplate. Upon his death, these are returned back to the Sovereign.

Check out the pictures of the 'Order of the Garter' service and Duchess' signature style below:

Catherine, Duchess of Cambridge leaves the Garter Service in a carriage at St George's Chapel in Windsor Castle in Windsor June 13, 2011.

Kate wore her grey Katherine Hooker coat dress, which she also wore to last year’s Order of the Garter ceremony over her Jenny Packham grey silk floral print dress (from the Santa Barbara polo match during her tour of Canada and the United States last year). Kate’s garments and accessories look brilliantly pulled together, it’s almost as if she’d shopped this outfit from scratch. Great at coordinating.