Kate Middleton's standout Stella McCartney dress at Archie's christening

The Duchess of Cambridge might just have stolen the show in a very fashion-forward look chosen for the christening of her nephew, Archie Harrison.

Kate Middleton wore a short pink Stella McCartney dress for the private event, which took place in a small chapel at Windsor Castle with just 25 guests. She paired the look with bold red heels and a statement headband, appearing more Blair Waldorf in Gossip Girl than a demure British duchess.

The knee-length dress is thought to be a recycled number that's been in Kate's wardrobe since 2009. It's believed she last wore it to the Queen's Christmas lunch in 2018.

While Meghan opted for a traditional look, Kate had some fun with her outfit. Photo / Instagram

And it featured what looks to be a current favourite neckline for the duchess: a pussy bow tie. It's reminiscent of the powder blue ensemble by Elie Saab she wore to Ascot last month, which also had a bow on the front.

And a purple ensemble from Gucci worn for an engagement in south London in March.

Kate's Elie Saab number at Ascot was also a standout look. Photo / Getty Images

The mother-of-three also gave a nod to her late mother-in-law by donning a pair of Princess Diana's pearl earrings.

Kate, 37, beamed for the camera as she elegantly posed on a chair in front of her husband Prince William - and appeared to pay tribute to her mother-in-law.

But she will have no doubt felt a bit emotional, remembering the christenings of her own children, Prince George, 5, Princess Charlotte, 4, and Prince Louis, 1.

The family picture comes as Harry and Meghan faced public backlash over their insistence at keeping son Archie Harrison's christening private.

Senior royals present included Prince Charles, Camilla, Prince William and Kate Middleton, but the Queen was not in attendance.

- Additional content, Daily Mail