Kate Middleton and Prince William’s desire for privacy has been even more zealously guarded as the Princess of Wales continues cancer treatment.

“It is really impressive how they are still able to command all this secrecy,” royal historian Amanda Foreman tells PEOPLE exclusively in this week’s cover story. “They are totally running this.”

The Princess of Wales, 42, largely remained out of the public eye for six months, recovering privately from her abdominal surgery in January before revealing in March that post-operative tests found cancer and that she was undergoing chemotherapy.

In her emotional health announcement, Kate called the news a “huge shock” and said that she and Prince William, 41, “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.” She added that “it’s taken us time to explain everything” to their children Prince George, 10, Princess Charlotte, 9, and Prince Louis, 6, “in a way that is appropriate for them, and to reassure them that I am going to be okay.”

She added, “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.”

Wary of leaks to the press, Princess Kate had been open about her cancer diagnosis to some, but other close friends and confidants were unaware. A former palace aide previously told PEOPLE: “The circle of knowledge was very tight.”

Kate made her first public appearance since Christmas at Trooping the Colour on June 15, forming a united front with the royal family at King Charles’ birthday parade. From the moment her carriage drew into view, all eyes were on the royal mom.

As the royals retreated behind the Buckingham Palace curtains after the pageantry, it is not Princess Kate who must support her husband as the future king but Prince William who must support her. 

“To use the late Queen’s language, they are each other’s strength and stay for all these years; she will continue to be a real source of strength for him as he prepares to be the next King,” says royal biographer Sally Bedell Smith. “But since this befell them, he has been a huge support for her — not only behind closed doors but also in going out in public and carrying out his job. Watching the two of them on the palace balcony, you could see their bond — and their bond with the children.”

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