“Apart from debilitating bouts of morning sickness and, of course, stays in the Lindo Wing at St Mary’s Hospital to deliver her babies, Catherine has fortunately avoided hospital for most of her life,” Mr Jobson explained. “As a teenager, however, when at Marlborough College she discovered a lump on the left side of her head, just under her hairline,” he added.

The author added that her mother took her to the hospital where the doctors removed it. “The school notified her parents immediately and her mother Carole took her to hospital, where she had surgery to remove it,” he wrote in the book.

However, the operation left a three-inch scar which several people noticed on Ms Middleton’s first solo engagement over two decades ago. The Buckingham Palace shared a brief statement that read, “‘The scar is related to a childhood operation.”

Meanwhile, the Princess said in June that she was making good progress as she was undergoing preventative chemotherapy. However, she was “not out of the woods”.

In a personal written message, Ms Middleton said she had been “blown away” by the thousands of kind messages from across the globe which followed her cancer announcement in March. “I am making good progress, but as anyone going through chemotherapy will know, there are good days and bad days,” her statement said.

She added, “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.” She said they had made a world of difference to her and her husband, heir-to-the-throne Prince William.

“My treatment is ongoing and will be for a few more months,” she said. “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,” she said on June 14.

The Princess of Wales was recently seen at the Wimbledon Men’s final in London as she walked onto the court to present the trophy to winner Carlos Alcaraz. A passionate tennis fan and player herself, Kate was greeted with a thunderous ovation as she entered the Royal Box at Centre Court, accompanied by her daughter Princess Charlotte and sister Pippa Matthews.