Kate Middleton and Prince William Are 'Going Through Hell,' Says 'Heartbroken' Designer Friend

One of Kate Middleton and Prince William's go-to designers is expressing concern for the couple amid the Princess of Wales' cancer treatment.

Amaia Arrieta, the designer behind many of the looks worn by the couple's children Prince George, 10, Princess Charlotte, 9, and Prince Louis, 6, through the years, told The Telegraph: "I'm heartbroken at the moment. I think they are going through hell."

"I hope they will be back. It's really personal," Arrieta added.

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."

Mark Cuthbert/UK Press via Getty

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.)

Arietta told The Telegraph, "Dressing the royals gives me so much pride, I really do care about how they look."

Less than two weeks after the Mother's Day photo controversy, Princess Kate appeared in a video to deliver a self-written speech announcing her cancer news. Post-operative tests from her "planned abdominal surgery" in January revealed that "cancer had been present," prompting her to start chemotherapy, the royal mom said.

Calling the health news a "huge shock," Princess Kate said that she and her husband "have been doing everything we can to process and manage this privately for the sake of our young family. As you can imagine, this has taken time. It has taken me time to recover from major surgery in order to start my treatment. But, most importantly, it has taken us time to explain everything to George, Charlotte and Louis in a way that is appropriate for them, and to reassure them that I am going to be okay."

Prince William, 41, has resumed royal duties and recently spoke about his wife and children for the first time since Princess Kate shared her health update.

"Do you mind if I ask how your wife and children are?" a woman asked the Prince of Wales following his visit to the charity James' Place Newcastle on April 30. 

"We're all doing well, thank you," he replied.

"And obviously Catherine?" the woman continued, to which William said, "We're all doing well."

Mark Cuthbert/UK Press via Getty

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The news of Princess Kate's diagnosis came weeks after her father-in-law, King Charles, announced on Feb. 5 that he was undergoing treatment for cancer. "During The King's recent hospital procedure for benign prostate enlargement, a separate issue of concern was noted. Subsequent diagnostic tests have identified a form of cancer," the palace said in a statement. "His Majesty has today commenced a schedule of regular treatments, during which time he has been advised by doctors to postpone public-facing duties. Throughout this period, His Majesty will continue to undertake state business and official paperwork as usual."