The Princess of Wales had been outside the public eye for six months — an unprecedented absence for a modern royal — so when her carriage came into view at King Charles’ official birthday parade, all eyes were on the royal mom. Stepping out with her children Prince George, 10, Princess Charlotte, 9, and Prince Louis, 6, Kate appeared both fragile and resilient as she continues chemotherapy following her cancer diagnosis, which she announced to the public in March.

“She looked vibrant and mounted and dismounted the carriage without losing a step,” says royal biographer Sally Bedell Smith.

On the Buckingham Palace balcony, the Princess of Wales exchanged loving glances with her husband, Prince William, and proudly reveled in her three children as the family of five struck a unified look in their coordinated ensembles. Her deepening bond with her father-in-law the King, who is also undergoing cancer treatment, was evident as they leaned in and chatted.

“She couldn’t have picked a better moment to reappear in public,” says Bedell Smith. “She didn’t seem to stop smiling. She looked so happy to be there. It was spellbinding to watch her.”

Aside from Kate’s personal health update and Trooping the Colour appearance, there have been encouraging signs of improvement. Princess Kate has been spotted running errands and planning activities for the children, including a day at the beach, where she captured in a photo to mark Father’s Day.

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

“There were three generations there,” Bedell Smith says of the royal family’s united front. “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.”

Princess Kate’s appearance couldn’t have come at a more opportune time, as rumors about her well-being had begun to recirculate. “Queen Elizabeth used to say, ‘I need to be seen to be believed.’ She said that before the days of online conspiracy theories, but she meant that in order to do the job of royalty, they need to be seen directly,” says King Charles’ biographer Catherine Mayer. “However difficult, or otherwise, this has been for Kate, appearing was an act of service under the terms of the institution she is part of.”

Despite a torrential English downpour, both the royal family and the public were touched to see Princess Kate standing strong before them.

“The family will take great comfort from that kind of support — that people did stick around to see them all in such ghastly weather is a real testimony to them,” says Anderson.