Kate Middleton's Commonwealth Day outfit sent a subtle but clear message to Queen Camilla - and not for the first time

Even the smallest outfit details can say an awful lot when it comes to the Royal Family, but it was one of the most obvious ones that caught my attention at the Commonwealth Day service. The Princess of Wales attended in a cobalt blue coat dress by British brand, Catherine Walker, whilst Queen Camilla was striking in scarlet.

These shades were radically different and I don't believe that was a coincidence. Looking back at all the Commonwealth Day services they've attended, there's only been occasion where the Princess and Queen stepped out even close to the same hue.

Matching outfits aren't against royal protocol and it does occasionally happen, but it's a sure-fire way to attract unnecessary direct comparison and could be seen as something of a faux pas. The Princess of Wales's decision to go for something very different ensured that the spotlight remained firmly on Queen Camilla.

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The late Queen Elizabeth used to deliberately choose outfits that made her stand out, with the Duchess of Edinburgh explaining, "She needs to stand out for people to be able to say, 'I saw the Queen.""

"Don't forget that when she turns up somewhere, the crowds are two, three, four… ten to fifteen deep, and someone wants to be able to say they saw a bit of the Queen's hat as she went past," Sophie added on the Our Queen at Ninety documentary.

According to former Prime Minister Boris Johnson's wife Carrie, Queen Elizabeth also left her a note informing her what she'd be wearing to dinner at Balmoral. This was a clever way of avoiding colour coordination and whilst I don't imagine for a moment that the Princess of Wales receives notes from Queen Camilla, I do think they might at least mention the colour they're thinking of wearing before an event.

The Princess's popularity and the "Kate effect" on fashion means that she is often the focus of headlines, whilst Queen Camilla has had a more complex relationship with the press over the years. Going for an entirely different colour outfit at the Commonwealth Day service meant that Kate wasn't overshadowing Her Majesty, who stood out in her gorgeous red look.

The Princess of Wales is always conscientious with her stepmother-in-law, showing a huge amount of respect to the senior royal. At the 2022 service, body language expert Judi James noted several gestures from the Princess of Wales to the then-Duchess of Cornwall that indicated this.

"Kate touched Camilla's arm with her left hand as an add-on gesture to suggest closeness and affection as they cheek-kissed," she claimed to The Mirror. "She also performed a huge 'act of inconvenience' to show respect, bending her knees to lower herself right down to plant her kiss on Camilla's cheeks."

The Royal Family might be a family, but there is a hierarchy and the Princess of Wales is seemingly very mindful of her place in it. Mostly she even steers clear of wearing the same overall colour as Queen Camilla, never mind the same shade.

In 2015 Her Majesty wore a slate-blue look and Kate was in pastel pink, whilst last year Camilla was in pink and the Princess of Wales wore bright red to the Commonwealth Day service. Look closely and you can often see this same pattern of not-matching ensembles at other events like Garter Day and Trooping the Colour too.