The Duchess of Cambridge joined members of the British and European Royal Families at the Order of the Garter service at Windsor Castle on Monday afternoon.
Kate, 37, wore a white coat dress by British fashion designer Catherine Walker with black piping on its Peter pan collar and bodice. She teamed it with a black hat by Lock & Co and matching clutch bag.
The mum-of-three arrived with the Duchess of Cornwall, 71, who wore a pale pink dress by her wedding dress designer Anna Valentine, and Sophie, Countess of Wessex, 54, who looked chic in a a white and coral outfit by Suzannah.
The British royal ladies were joined by Queen Letizia of Spain and Queen Maxima of the Netherlands.
Queen Maxima turned to one of her go-to fashion designers Claes Iversen for the service. She matched her royal counterparts in a pale pink caped and belted dress, with a matching saucer-style hat.
Before the service, their husbands King Felipe VI of Spain and King Willem-Alexander of The Netherlands were installed as Supernumerary or ‘Stranger’ Knights of the Garter.
The Order includes the Queen, who is Sovereign of the Garter, the Prince of Wales and several senior members of the Royal Family, and twenty-four knights or ladies chosen in recognition of their work.
They are chosen personally by the Queen to honour those who have held public office, who have contributed in a particular way to national life or who have served the monarch personally.
Supernumerary Knights are overseas monarchs appointed to the Order, and are in addition to the twenty-four knights or ladies.
The Duke of Edinburgh, the Duke of Kent, Princess Anne, the Duke of Gloucester, Princess Alexandra, Prince Andrew, Prince Edward and Prince William are all additional royal Knights and Ladies Companions.
The Duke of Cambridge received the honour in April 2008, becoming the 1,000th Knight of the Garter.
William joined his father Charles for the procession from Windsor Castle to the service at St George’s Chapel.
The Queen made the journey by car, wearing full ceremonial regalia, which include a dark blue velvet mantle embroidered with the Order of the Garter insignia and a red sash and black velvet Tudor style bonnets with ostrich and heron feathers.
Following the service, members of the Royal Family made their way back to the castle in carriages.
The Queen and the royals will be out together again this week at Royal Ascot.