There are few occasions when the royals can get dressed to the nines for family celebrations, so you'd expect Prince Edward and the Duchess of Edinburgh's 1999 wedding to be one of those instances.
Edward's brothers Prince Charles and Prince Andrew tied the knot several years beforehand, in 1981 and 1986 respectively, and the ceremonies were full of pomp and circumstance. However, Queen Elizabeth II's son and the PR executive, then known as Sophie Rhys-Jones, wanted a more informal wedding at St George’s Chapel at Windsor Castle, without any ceremonial state or military involvement.
Shortly after their engagement, which took place just before Christmas in 1998, Edward and Sophie both agreed they wanted a "low key" ceremony, with the royal adding in an interview: "There's no such thing as a private wedding but I hope that it will be predominantly a family wedding."
To reflect the relaxed atmosphere, Sophie and Edward supposedly set some rules in place when it came to wedding guest fashion – but several of the royal family didn't comply! The couple asked their family and friends to wear evening gowns and smart attire but no headpieces, which are normally customary.
Some of Edward's family chose to continue with tradition by wearing beautiful hair accessories. While Princess Anne opted for a small green hair accessory and the Queen wore a lilac feathered fascinator that tied in with her lace dress, the Queen Mother went one step further.
She was pictured in a purple hat with bold feathered detailing, while the guests around her were noticeably hatless. It is thought that this is because hats were one of her staple items of clothing that she rarely went without.
For the big day, Sophie looked beautiful in a silk organza Samantha Shaw dress paired with a full-length veil made of silk tulle and crystals. It was held in place by her beautiful diamond tiara, which was originally from the Queen's private collection and was made up of four open scrollwork motifs.
To finish off her outfit, the Duchess added a black and white pearl necklace and matching drop earrings which were a wedding gift from Prince Edward. She later took her jacket off to reveal her second bridal look, which was a long-sleeved gown with a sparkly waist.
The royal couple are now parents to two children: Lady Louise Windsor and James, Viscount Severn, born in 2003 and 2007 respectively.
And despite the lack of hats at her own wedding, Duchess Sophie has been spotted with some pretty impressive headpieces when she's been a guest at other people's nuptials. Take her pastel pink fascinator at Mike and Zara Tindall's wedding, and her leopard print feathered hat at King Charles and Queen Camilla's civil ceremony, for example!
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