For all her previous appearances at Royal Ascot, the Princess of Wales has worn pretty white or pastel dresses. But that was then - this year she's in attendance for the first time in her newly elevated position and it was, evidently, time for a change. Out with the soft and feminine, in with the pop of power colour.
Arriving for the fourth day of racing, Catherine wore a bright red Alexander McQueen dress with a hat by Phillip Treacy. In her primary coloured-outfit, she stood out among the other Royal women - Queen Camilla, the Duchess of Edinburgh, Princess Beatrice and Princess Michael of Kent - who had all opted for delicate shades of white and pink.
She may have switched up her colour palette, but the overall feel of the Princess's outfit was elegant, timeless and feminine; with its giant floral decoration, her hat had a sophisticated vintage effect while her dress came with McQueen's signature tailored flourishes - like puffed sleeves, a nipped waist and carefully sculpted neckline - but with a swishy pleated skirt which stopped the look feeling too serious.
Alexander McQueen, which is designed by Sarah Burton, is one of Catherine's most-loved clothing labels. Burton designed the Princess's wedding dress and the embroidered gown which she wore for the Coronation of King Charles in May.
The Princess added three new accessories to her Royal Ascot ensemble, creating a high/low effect by mixing designer and high street.
She debuted a new clutch bag by the luxury French house Hermes. The "Rio" clutch bag, which Catherine carried in red to match her outfit, is a discontinued style so must either have been bought second-hand by the Princess or has been in her private wardrobe or family collection for years.
It is the first time she has worn anything from Hermes, which holds a special position in the Royal family as purveyor of silk scarves to the late Queen Elizabeth II and of silk ties to King Charles going back several decades.
Over the years, Hermes paid tribute to the late Queen's love of its scarves many times by issuing special styles in her honour to celebrate her landmark birthdays and jubilees. For the King, Hermes ties are an opportunity to bring some wit to his outfits, via lighthearted motifs like owls, cats, clouds and dinosaurs.
It seems that Catherine also has a new favourite shoe brand. For the second time this week, she debuted a new pair of shoes by Jennifer Chamandi, a British-Lebanese former banker whose stiletto designs come with a signature "eye of the needle" heel. On Monday she wore the label's two-tone "Vittorio" heels while on Friday, she opted for the "Lorenzo" pumps without the distinctive band across the top of the foot.
The Princess of Wales added a more democratic touch to her upscale ensemble with a pair of statement earrings from Sezane, the almost-high street French label which has become a favourite source of bold jewellery for her in recent years. Her opulent gold hoops with black beading are no longer for sale but would have retailed for around £75.
Many of the Princess of Wales' formal looks have felt like they have been pushing the fashion envelope recently. Friday's Alexander McQueen was a departure from the ultra-polished tailoring and embellishment in favour of a more classically ladylike direction.
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