Kate and William are 'going through hell': Designer behind many of George, Charlotte and Louis' clothes says she's 'heartbroken' for Princess of Wales as she faces cancer battle

Prince William and Princess Kate are 'going through hell' amid the Princess of Wales' cancer diagnosis as they struggle to come to terms with the news that any family dreads, a designer close to the family has said.

Amaia Arrieta, a children's clothing designer behind many of the outfits worn by Prince George, Princess Charlotte and Prince Louis, who became close with the Wales' after the birth of their eldest son, has described how the family are struggling as Kate battles the disease.

Ms Arrieta, herself a mother-of-three, told the Telegraph she has been left 'heartbroken' by the news after years of supplying the royal children with clothes for their wardrobes. 

'I'm heartbroken at the moment, I think they are going through hell,' she said. 'I hope they will be back. It's really personal.'

Kate, 42, revealed she was battling cancer just weeks after her father-in-law, King Charles, announced his own diagnosis with the illness.

It was less than a fortnight after a Mother's Day photo sparked an online frenzy around the world after royal fans became convinced the picture had been edited.

The Princess of Wales later put out a statement confirming she had experimented with editing just 'like many amateur photographers'.

She and nanny Maria Teresa Turrion Borrallo have been picking out Amaia designs for the children, aged ten, nine and six, since George was just a baby.

The Spanish-born designer told the paper dressing the royals brings her 'so much pride' as Charlotte prepared to celebrate her ninth birthday last week.

She first saw her designs in use in a portrait of Prince George from 2014, in which he wore Amaia shorts and knee-high socks. 

Recalling the moment she saw the photo, on the cover of a Hello! magazine in Waitrose, Ms Arrieta said: 'That was a huge moment because they had been coming to us but you never know if they'll actually wear it.' 

She has since provided clothing worn at the late Queen's Platinum Jubilee, as well as in official photographs, at Christmas and for royal events throughout the year. 

Most recently, Princess Charlotte wore an Amaia skirt in the controversial Mother's Day snap.

Shortly afterwards, on March 22, Kate released an emotional video in which she told the public she is battling cancer. 

She, the Prince of Wales, 41, and their three children, all missed the Easter Sunday service at St George's Chapel at Windsor Castle, following the announcement, despite attending last year.

The family spent the Easter holiday together as they adjusted to Kate's diagnosis, which was discovered in post-operative tests after major abdominal surgery.

In the message revealing the diagnosis last month, Kate said: 'This of course came as a huge shock, and William and I 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 OK.'

Since revealing the diagnosis, the Prince and Princess of Wales are said to be 'enormously touched' and 'extremely moved' by the public's warmth and support.

As King Charles returned to limited public duties in recent days, it has not yet been confirmed when Kate will be back to business.

Prince William has carried out limited public engagements as he cares for his wife and children, visiting a youth centre in west London last month.