Kate Middleton Has Been Following This Casual Fashion Rule Since Before She Was a Royal

It's admittedly taken some convincing to welcome certain '90s and '00s trends back into our wardrobe. But, while items such as vests and low-rise jeans still feel questionable, we have hung onto a few key pieces from way back when — and, so it seems, has Kate Middleton.

Striped shirts, for instance, were a must-have for the royal back in 2007, long before she and Prince William ever said "I do." Now, over 13 years later, she continues to work them into her outfits, stepping out in the wardrobe staple every few months.

It's easy to see why Kate gravitates towards this simple style: it's timeless and easy to dress both up and down. Striped shirts have definitely become a go-to and rule of sorts for the duchess. Whenever she's having a laid-back, casual day, her outfit tends to consists of a navy and white option, which she pairs with jeans and a crisp pair of white sneakers.

Still, there have been numerous ways Kate has worn striped shirts over the years. Take a look at some of her best outfits, ahead.

2007

While out in London, Kate wore a very aughts combo of a simple striped tank top, black skinny jeans, a chunky belt, and some wedges.

2007

This shirt style also happens to be Kate's choice for a variety of activities. She chose to wear a striped tee and leggings while taking part in a training session with the Sisterhood cross-channel rowing team.

2012

After Kate officially became the Duchess of Cambridge, she was still loving this classic style. At the 2012 Olympics in London, she layered a striped sweater under a navy blazer, completing her outfit with skinny jeans and those signature wedges.

2013

When it works, it works! Kate pretty much repeated that same outfit a year later, while attending a SportsAid Athlete Workshop.

2014

Kate didn't bother with skirt suits and heels while watching a charity polo match. Instead, it was a long-sleeved striped tee to the rescue, styled with jeans and flats.

2015

Kate sure loves the navy and white combo, but sometimes she switches up the shade, opting for a royal blue.

2015

She may be wearing layers, but Kate's striped shirt still peeked out as she attended the America's Cup World Series.

2017

A splash of red made Kate's simple outfit all the more eye-catching as she hosted a reception ahead of the London Marathon.

2017

We wouldn't be surprised if Kate's closet was full of long-sleeved striped tees in all sorts of colors. While visiting Germany, the royal made sure to pack a light blue option.

2019

Of course, the duchess doesn't always dress down her striped shirts. While launching the King's Cup Regatta, she chose to style a sweater version with wide-leg navy pants and heels. So simple yet so sleek.

2019

The same bottoms made an appearance a few months later, but Kate switched up her top. She went a little more modern with a multi-colored, ruffled and peplum design, but gave things a casual twist with white sneakers.