Kate Middleton and Prince William's Privacy Needs Are Stronger Than Ever: 'Impressive How They Command Secrecy' (Exclusive)

The Prince and Princess of Wales try to create as normal a life as possible for their children

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."

Related: Prince George Catches Kate Middleton and Prince William Exchanging a Look of Love at Trooping the Colour

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."

The "kiddies" — as Princess Kate calls Prince George, Princess Charlotte and Prince Louis — brought the charm at Trooping the Colour, reminding everyone that they’re a family first.

"There were three generations there," says Bedell Smith. "It was a perfect way for Kate to reenter the public sphere at this event, which is so full of tradition going back hundreds of years and is a symbol of the continuity of the royal family."

Adds a royal source: "Family is really important to the Princess of Wales, and she wanted to be there to support her family."

Related: Why Kate Middleton's Trooping the Colour Outing Doesn't Signal a Return to Royal Duties amid Cancer Treatment

Princess Kate confirmed her Trooping the Colour attendance on June 14 in a personal update on her health. In a self-written message accompanied by a portrait beneath a tree near her home in Windsor, she reassured that she is "making good progress" despite the challenges of chemotherapy. She openly spoke about the ups and downs of her journey and expressed gratitude for the overwhelming support she has received. Yet, she cautioned, she is not "out of the woods yet."

Reserved Kate, who has been re-prioritizing her life over the last three months, shared that she’s focusing on her own needs while finding comfort in her family.  William is "pleased" that his wife is "starting to engage with the work and projects that are important to her," a palace spokesperson said.

However, the Trooping appearance does not mean she has resumed royal work; any outings in the near future will be based on when she feels able and with the support of her medical team.

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Those close to the princess say that she also finds relief in the mundane activities of daily life.

"The children won’t remember Mummy shaking hands or really care," says Foreman. "But they will recall Mummy making cakes [or when] she went off to the local shop and bought something or took them somewhere."

The royal has been spotted running errands and planning activities for George, Charlotte and Louis, including a day at the beach, where she took a photo of her husband and children for Father's Day.

"When you’re going through something that is not routine, it is great to have that anchor of normality," adds Ailsa Anderson, former press secretary to Queen Elizabeth.

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