Smiling Kate leaves William in royal flush at Garter Day parade

A smile from Kate left William unable to control his emotions as he processed though the grounds of Windsor Castle with other Knights and Ladies of the Order of the Garter.

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

The royal couple exchanged greetings as Kate stood with the Duchess of Cornwall watching the pomp and pageantry of the Garter procession held before the annual service.

Camilla beckoned the Duchess forward so some of the almost 6,000 people who had gathered in the Castle’s precincts to watch the colourful spectacle, could get a better view of the newest member of the Royal Family.

Kate grinned broadly as William approached her vantage point in the Galilee Porch of St George’s Chapel, walking stride for stride next to the Prince of Wales.

The Duke wore the Order’s lavish blue velvet robes and black velvet hat with white plumes like the other Garter Knights in the procession. He gave a toothy smile in return and then blushed as he turned to talk to his father.

The Duchess looked chic in a dove-grey coat with matching fascinator and watched as the Queen – sovereign of the order – and Duke of Edinburgh, last in the long procession, passed by.

When William was made a Royal Knight of the Order in 2008, Kate was there to witness his first procession and collapsed into a fit of giggles with Prince Harry.

But yesterday, without the influence of her husband’s younger brother, the Duchess proved much more supportive.

Royal Knights or Ladies of the Order include the Duke of York, the Earl of Wessex and the Princess Royal.

The Order has up to 24 Companion Knights who are usually drawn from those who have held high office.