Order of the Garter service: Queen joined by Duchess of Cambridge and members of royal family for annual event in Windsor

The Duchess of Cambridge joined senior members of the royal family and foreign monarchs to watch the traditional annual Garter Day procession in Windsor today.

Two Queens accompanied Kate and Britain's royal ladies to watch their husbands on parade at the annual event, which celebrates the most senior order of the chivalry in the UK.

Queen Maxima of the Netherlands and Queen Letizia of Spain stood at the Galilee Porch outside St George’s Chapel in Windsor Castle with the Duchess of Cornwall, the Duchess of Cambridge and the Countess of Wessex to see the procession of the Knights of the Garter.

The Dutch King Willem-Alexander and his Spanish counterpart King Felipe were installed as companions of the ancient Order of the Garter in the chapel after an earlier investiture up the hill in the state apartments.

Founded by Edward III in 1348, the Most Noble Order of the Garter is the most senior order of knighthood in the British honours system, outranked in precedence only by the Victoria Cross and the George Cross.

For the occasion, the duchess cut a chic figure in a perfectly tailored white coat dress with black trim by Catherine Walker, a British label often favoured by the duchess, which was also a go-to designer for her late mother-in-law, Princess Diana.

Argentine-born Maxima, 48, and Letizia, 46, stood chatting with Kate, the Duchess of Cornwall and the Countess of Wessex outside the chapel before the procession began.

Wearing the lavish velvet robes, glistening insignia and plumed hats of the Order of the Garter, the Queen and the royal knights processed through the grounds of Windsor Castle.

Camilla, 71, wore a pale pink Anna Valentine coat dress with a Philip Treacy hat, while Sophie, 54, sported a Suzannah dress and Jane Taylor hat.

They stood smiling with Kate, Maxima in particular beaming, as their husbands walked by in the procession.

Further down the hill, Felipe, 51, waved merrily at Spanish journalists as the procession neared the chapel.

The Queen, accompanied by Princess Alexandra, travelled by car to the chapel, a few hundred yards down the hill from her apartments, behind the knights’ procession.

Hundreds of spectators watched the Garter Knights walking through the grounds of the castle in the summer sunshine, wearing their blue velvet robes and black velvet hats with white plumes made from ostrich feathers.

The Queen was joined by Prince Charles, the Duke of Cambridge and other senior royals in St George's Chapel for the service.

Former Prime Minister Sir John Major, Lord Phillips of Worth Matravers, a past president of the Supreme Court, and Admiral Lord Boyce, a former head of the UK's armed forces are also Garter knights and were part of the procession in front of the royals.

King Felipe VI and Willem-Alexander of the Netherlands were installed in the chapel as supernumerary, or stranger, Knights of the Garter.

Felipe was appointed by the Queen during his July 2017 state visit while Willem-Alexander received the honour during his state visit in October 2018.

Earlier in the day there was a private Investiture in the Garter throne room at Windsor Castle, where a new Lady Companion, former Olympic athlete Lady Mary Peters, and a Knight Companion, Robert Gascoyne-Cecil, the Marquess of Salisbury, were invested with the Order's insignia by the Queen.

Recipients of the honour are chosen because they have held public office, contributed to national life or served the sovereign personally.

The appointment of Knights of the Garter is in the Queen's gift and is made without consulting ministers.

The Queen is sovereign of the order and a number of other British and foreign royals are additional knights of the order, including Philip, Charles and William.

The foreign monarchs were invested with the insignia of the Order by the Queen in the castle's garter throne room and during the service were installed, or formally seated, in the chapel's quire.