James Middleton vows to climb this "mountain" with sister Kate Middleton in a moving post

The Princess of Wales has been diagnosed with cancer and is in the early stages of preventative chemotherapy.

The 42-year-old mother of three broke the news in a televised video message, giving a rare update on her health and telling the world that "it had been an incredibly tough couple of months for [the] entire family."

"[The diagnosis] of course came as a huge shock", Kate stated in the video message, explaining how she and Prince William had been doing everything possible "to process and manage this privately for the sake of [their] young family."

"As you can imagine, this has taken time," she continued. "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."

"As I have said to them; I am well and getting stronger every day by focusing on the things that will help me heal; in my mind, body and spirits," she continued, crediting the people around her for the "love, support and kindness" shown to her.

Members of the royal family, including Prince Harry and King Charles have released messages of support to the Princess of Wales. So too did the Middleton family, with Kate's brother James posting a tribute to his sister on social media.

Posting a childhood photograph of the two of them hiking on Instagram, James penned the moving message: "Over the years, we have climbed many mountains together. As a family, we will climb this one with you too."

"We hope that you will understand that, as a family, we now need some time, space and privacy while I complete my treatment," the Princess of Wales stated in her televised message. "My work has always brought me a deep sense of joy and I look forward to being back when I am able, but for now I must focus on making a full recovery."

Our thoughts are with the Princess of Wales as she continues her recovery.

We will continue to update this story.