Princess Kate, 42, has dressed her children in clothes by the Spanish-born designer since Prince George was a baby — something Arietta discovered while grocery shopping.

“The first time I realized Prince George was wearing my designs, I was in Waitrose and saw the picture of him on the cover of Hello! magazine,” she recalled. “That was a huge moment because they had been coming to us, but you never know if they’ll actually wear it.”

She continued to work closely with the children’s nanny, Maria Teresa Turrion Borrallo, on outfits for George, Charlotte and Louis, including momentous occasions that make the front page such as Princess Eugenie’s 2018 wedding, birthdays and the royal family’s annual Christmas Day outing to church.

“It’s often a very tight deadline,” she reveals. “We would do anything for them…the children always look amazing in the end.”

Princess Charlotte, who celebrated her 9th birthday on May 2, recently wore a skirt by Amaia London in the photo released to mark Mother’s Day. (The image prompted Kate to release a statement after it was removed by multiple news agencies due to suspicions of manipulation. “Like many amateur photographers, I do occasionally experiment with editing. I wanted to express my apologies for any confusion the family photograph we shared yesterday caused,” she said.)