Kate Middleton’s birthday: Prince William shares a deeply personal tribute to mark his wife's 43rd birthday

Along with a beautiful black and white photograph of Catherine, Princess of Wales, Prince William wrote: “To the most incredible wife and mother. The strength you’ve shown over the last year has been remarkable. George, Charlotte, Louis and I are so proud of you. Happy Birthday, Catherine. We love you. W.”

The photograph of Catherine, Princess of Wales, was taken by Matt Porteous in Windsor last year. Matt Porteous was of course the man behind the deeply personal video taken of Catherine, Princess of Wales, Prince William, and their children to reveal that she had finished her treatment for cancer.

King Charles and Queen Camilla had earlier shared a photograph of Catherine, Princess of Wales on Christmas Day on their Instagram stories and wrote: “Happy Birthday to The Princess of Wales,” followed by a birthday cake emoji.

It is not officially known how Catherine, Princess of Wales intends to spend her birthday, but it is thought that she is likely to celebrate it quietly with Prince William, Prince George, Princess Charlotte and Prince Louis at their Norfolk home, Amner Hall.

After undergoing abdominal surgery in January last year, it was then announced in March the Princess of Wales was receiving preventative chemotherapy for cancer.

Catherine, Princess of Wales said in her video message that “I wanted to take this opportunity to say thank you, personally, for all the wonderful messages of support and for your understanding whilst I have been recovering from surgery.

“It has been an incredibly tough couple of months for our entire family, but I've had a fantastic medical team who have taken great care of me, for which I am so grateful.

“In January, I underwent major abdominal surgery in London and at the time, it was thought that my condition was non-cancerous. The surgery was successful. However, tests after the operation found cancer had been present. My medical team therefore advised that I should undergo a course of preventative chemotherapy and I am now in the early stages of that treatment.

“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.

“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.

“Having William by my side is a great source of comfort and reassurance too. As is the love, support and kindness that has been shown by so many of you. It means so much to us both.

“We hope that you will understand that, as a family, we now need some time, space and privacy while I complete my treatment. 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.

“At this time, I am also thinking of all those whose lives have been affected by cancer. For everyone facing this disease, in whatever form, please do not lose faith or hope. You are not alone.”

Just before Trooping the Colour in June, Catherine, Princess of Wales gave a health update.

She released a photograph of herself, taken by Matt Porteous, she was photographed in the gardens of Windsor, standing beneath a willow tree, and in the photo, she is seen looking up into the sky. Catherine, Princess of Wales released a statement alongside the photo which read: "I have been blown away by all the kind messages of support and encouragement over the last couple of months," she said. "It really has made the world of difference to William and me and has helped us both through some of the harder times."

She also said: “ I am making good progress, but as anyone going through chemotherapy will know, there are good days and bad days. On those bad days, you feel weak, tired and you have to give in to your body resting. But on the good days, when you feel stronger, you want to make the most of feeling well.”

“My treatment is ongoing and will be for a few more months. On the days I feel well enough, it is a joy to engage with school life, spend personal time on the things that give me energy and positivity, as well as starting to do a little work from home.

“I’m looking forward to attending The King’s Birthday Parade this weekend with my family and hope to join a few public engagements over the summer, but equally knowing I am not out of the woods yet.

“I am learning how to be patient, especially with uncertainty. Taking each day as it comes, listening to my body, and allowing myself to take this much needed time to heal.

“Thank you so much for your continued understanding, and to all of you who have so bravely shared your stories with me.” The Princess of Wales signed off the statement with her initial C.”