King Charles coronation: Kate’s headpiece designed by Jess Collett and Alexander McQueen

Princess Catherine turned the coronation fashion rulebook on its head as she also honoured the late Princess Diana.

Britain's Prince William, Prince of Wales, Princess Charlotte, Prince Louis, Britain's Catherine, Princess of Wales, Prince Edward, Duke of Edinburgh. (Top L to R) James, Earl of Wessex, Lady Louise Windsor, Prince Richard, Duke of Gloucester and Birgitte, Duchess of Gloucester attend the Coronation of King Charles III and Queen Camilla

While King Charles and Queen Camilla stole the show with their astonishing ceremonial garb, Prince William, Princess Catherine and their kids were nevertheless strikingly dressed - the adults’ darker and more coloured outer robes a stunning contrast to the pale tones of the King and Queen.

Under his plush Order of the Garter robe - the same highly exclusive cape sported by his uncles - the Prince of Wales was wearing the Ceremonial dress uniform of the Welsh Guards.

Catherine, Princess of Wales dazzled in a crystal lead embrodiery headpiece. Picture: Getty Images

Under her eye-catching blue and red cape with white ribbons, reflecting the colours of the Union flag, Catherine wore an Alexander McQueen dress and headpiece - and daughter Charlotte was similarly outfitted by the designer.

Princess Catherine’s elaborate headpiece, which she wore instead of a tiara or a floral crown, sent fashion watchers into a frenzy.

The crystal lead embroidery headpiece in the shape of leaves was designed by milliner Jess Collett and Alexander McQueen, Vogue Australia reports.

Collett who has been working as a couture milliner for the past 25 years after receiving a life-changing loan from King Charles’ Princes Trust charity, which supports young people who are struggling with school or work.

Princess Catherine’s earring were a tribute to Prince William’s mother, the late Diana, Princess of Wales. Picture: AFP

The Princess’ earrings were a touching tribute to Prince William’s late mother, with the pearl and diamond pieces belonging to Diana, Princess of Wales.

Both dresses were of ivory silk crepe - Catherine’s with silver bullion and thread work embroidery featuring rose, thistle, daffodil and shamrock motifs, to signify the four nations of the United Kingdom.

Louis wore a blue doeskin tunic by Dege and Skinner while Prince George, in his role as a page of honour, was in striking red.

Britain's Prince William, Prince of Wales, Princess Charlotte, Prince Louis and Britain's Catherine, Princess of Wales attend the coronations of Britain's King Charles III and Britain's Queen Camilla at Westminster Abbey. Picture: Getty

Prince William also had a key role at the Coronation.

He pledged to be Charles’ “liege man of life and limb” - the only prince to do so, unlike previous coronations where a series of dukes would swear an oath of homage.

In a touching moment, William kneeled before his father about halfway through the ceremony.

Placing his hands between the King’s hands, the heir to the throne recited: “I, William, Prince of Wales, pledge my loyalty to you and faith and truth I will bear unto you, as your liege man of life and limb. So help me God.”

Called the Homage of Royal Blood, the “words of fealty” echo the vow made by his late grandfather Prince Philip to Queen Elizabeth in 1953 when he also vowed to be her “liege man of life and limb.”

Catherine, Princess of Wales and Prince William, Prince of Wales with Princess Charlotte and Prince Louis. Picture: Getty

Body language expert Dr Louise Mahler said:” William spoke. It was short and sharp. William kissed his father and Charles smiled warmly and seemed to mutter ‘Thank you’. All the words in Spare seemed to fly to the wind in this moment.”

The change in tradition avoids the awkwardness of Prince Harry and Prince Andrew having to do the same.

Prince William, Prince of Wales, Catherine, Princess of Wales, Prince Louis and Princess Charlotte arrive for the Coronation. Picture: Getty

Prince William, the monarch’s 40-year-old eldest son and heir took on Charles’ former mantle of the Prince of Wales after the late Queen’s death, stepping up into a more elevated role.

The Prince and Princess of Wales are seen as the most popular royals. Although not born into royalty, 41-year-old Catherine in particular is seen as a standard-bearer for the modern House of Windsor.

The couple joined the rest of the royals in the congregation, at the front, as the service got underway.

As heir to the throne and a future king, Prince William watches a ceremony he will one day be at the centre of himself.

William also made an appearance as the Stole Royal as the Robe Royal was presented to the King.

The Prince of Wales assisted both the Baroness Merron and the bishops in placing the robe on King Charles.