During last week's Royal Ascot, Meghan Markle looked positively flawless (no surprise there) in a white Givenchy shirtdress dress, a Philip Treacy fascinator, and a pair of simple black pumps.

At first glance, her heels appear ordinary—something that would garner sister-in-law Kate Middleton's approval—but upon closer inspection, her shoes are noticeably a size too big. It's a fashion oddity that Meghan has been quietly practicing since her engagement to Prince Harry.

Meghan Markle
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According to fashion expert Harriet Davey, there's perfectly logical explanation behind her rotation of ill-fitting pumps.

Meghan Markle
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"Celebs often go a size up, or even two, in the shoe department when they're at an event or on the red carpet and it's for one reason we can all relate to—to avoid blisters," Davey told The Sun. "There's nothing worse than uncomfortable shoes (we've all been there on a night out) and when celebs like Meghan are wearing heels for a long period of time their feet can often swell up."

That swelling not only increases your chances of developing blisters, but also bunions if you make a habit of wearing heels that are too tight.

Meghan Markle
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It all sounds practical in theory, but how does Meghan manage to walk without looking like a child prancing around in her mom's high heels? Davey has a secret:

Meghan Markle
Credit: Samir Hussein/WireImage

"A trick of the trade is to stuff the toe with padding like tissue or cotton wool, and this can be taken out once they feel like they need a bit more room in their shoes," she explained.

Well, there you have it. Time to size up the next time you go shoe shopping, ladies.