Kate Middleton and Prince William are 'going through hell,' says partner.

Kate Middleton and Prince William are “going through hell,” according to their close partner, Amaya Arrieta.

Arrieta, who has worked as a stylist for Kate Middleton and Prince William's three children since Prince George was a baby, shared the heartbreaking news for the couple after the princess was diagnosed with cancer.

Arrieta's statements indicate the seriousness of the situation

“I'm devastated right now, I think they're going through hell, and I hope they come back. It's a really personal thing,” Arrieta told The Telegraph.

The children's clothing designer, who owns the eponymous company Amaia, has so far avoided revealing information about the couple.

While it's not clear what prompted her to make this revelation — especially since the princess is still receiving chemotherapy for her condition — Arrieta's comments indicate the seriousness of the situation.

“I really care about their appearance.”

Elsewhere, Arrieta also addressed her role as fashion designer for Prince George, Princess Charlotte and Prince Louis.

She told the agency: “Dressing as the royal family gives me a lot of pride. I really care about their appearance.”

Arrieta said she works closely with the children's current nanny, Maria Borrallo, to dress the children.