Knee-length dresses, fascinators and modest necklines are some of the classic styles you can expect royal wedding guests to wear for their friend's or family's big day.
The Princess of Wales defied expectations when she stepped out for Prince William's friend Nicholas van Cutsem's wedding with Alice Hadden-Paton in August 2009 in a silky slip dress. Two years before marrying into the royal family, Kate (née Middleton) was more daring with her fashion choices, and she showed this off perfectly at The Guards Chapel at Wellington Barracks.
The 27-year-old's luxe silver satin dress was covered with a delicate floral brocade pattern which wouldn't look out of style today – just look at Victoria Beckham's floor-length silk mother-of-the-groom dress at Brooklyn Beckham's wedding for proof.
To achieve a more demure look, she layered it underneath a cornflower blue coat by Jane Troughton with a buttoned waist enhancing her silhouette.
Styling her brunette hair in long curls, the Princess added a grey and purple fascinator, alongside black heels and a matching clutch. Meanwhile, William served as an usher, looking dapper in a morning suit with striped grey trousers, a black tailcoat, a grey waistcoat and a purple tie.
Nicholas was a close childhood friend of both Prince William and Prince Harry, and they continue to share a close friendship today. The business developer is Prince Louis' godfather and his daughter Florence van Cutsem was a bridesmaid at Prince Harry's wedding in 2018.
This was not Kate's only glamorous wedding guest appearance before marrying Prince William. She attended Nicholas' brother Hugh van Cutsem's nuptials with Rose Astor at Burford Parish Church in June 2005 in a lace pencil skirt by Karen Millen with a cream blazer.
Meanwhile, in October 2010, she looked beautiful in a blue Issa dress paired with a black jacket and feathered hat for Harry Meade and Rosie Bradford's nuptials. What fans didn't know at the time, was that she was already engaged to William – and when the couple announced the news weeks later with a photocall at St James's Palace, the future Princess wore a similar royal blue Issa dress.
Photographer and AFP employee, Ben Stansall, recalled the "crazy" photocall in an interview with HELLO!. "It was incredible. I just remember thinking, 'I've never seen this much light from the cameras before. This is absolutely, absolutely crazy.'
"A lot of people were talking about whether Catherine would be wearing Princess Diana's ring. Then they came in and it was just a constant stream of light and flashes."
Blue has been one of Kate's go-to's over the years, and she has often made public appearances with her husband and three children Prince George, Princess Charlotte and Prince Louis in coordinating ensembles.
Not only does it perfectly tie in with her sapphire and diamond engagement ring, which Prince William presented to her during a trip to Kenya in 2010, but it also symbolises stability, peace, wisdom and serenity.