The daughter of the Earl and Countess of Wessex arrived at Westminster Abbey alongside the Queen's fellow grandchildren, including Prince William and Prince Harry, Princesses Beatrice and Eugenie, Zara Tindall and Peter Phillips and Louise's 14-year-old brother, James, Viscount Severn.
WATCH: All about the Queen's granddaughter Lady Louise Windsor
Many of the royals chose to honour the Queen through their carefully curated fashion ensembles, be it through wearing a mourning veil, adorning their ears with pearls, wearing the late monarch's jewellery or opting for sentimental brooches - but Lady Louise made a surprising nod to Princess Diana with one of her elegant accessories.
Lady Louise Windsor looked immaculate in a sleek black ensemble
Lady Louise looked beautiful in a flutter-sleeve dress by Theory, coined the 'Godet V-neck Recycled Polyester Midi Dress,' and pointed heels.
Featuring a slim-fitting waistband, a deep midnight shade, and feminine layers of sheer fabric, the number was a practical choice for the historic event.
The young royal crafted her golden locks into a timeless low bun with intricate wavy detail, held in place by a bow-clad velvet headband by royal-favourite milliner Jane Taylor London.
Lady Louise opted for the label's £569.80 classic headband, fondly named the "Diana" headband, which could have been named as such in memory of the late and former Princess of Wales.
Lady Louise wore the 'Diana' headband from Jayne Taylor London
The Countess of Wessex has exclusively worn Jane Taylor’s designs since 2009, so it comes as no surprise her daughter turned to the same millinery to craft her statement hairpiece.
The Queen's granddaughter also made an incredibly special tribute to the late Queen Elizabeth II, and her grandfather Prince Philip as she stood Vigil on Saturday evening in Westminster Hall.
The Queen's grandchildren attended a vigil at Westminster Hall
The university student appeared to be wearing a silver necklace displaying a horse pendant, as she joined her fellow grandchildren around Her Majesty's coffin. The sweet accessory was a moving nod to her and her grandparents' shared love of horses.
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