The Princess of Wales was joined by her three children as she attended Saturday’s Trooping the Colour ceremony, marking her first public appearance after revealing her cancer diagnosis in March.
Kate, 42, has been receiving treatment for an unspecified form of cancer since February, when the disease was discovered after she underwent abdominal surgery.
The senior royal made her first public appearance of the year for a traditional parade through London for the King’s official birthday celebrations.
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Prince George, 10, Princess Charlotte, nine, and six-year-old Prince Louis travelled with Kate in a horse-drawn glass carriage.
She was surrounded by other members of the family, with her husband the Prince of Wales, Colonel of the Welsh Guards, on horseback, along with the Princess Royal, Colonel Blues and Royals, and the Duke of Edinburgh, Colonel Scots Guards.
King Charles, who is also being treated for an undisclosed form of cancer, inspected the troops alongside Queen Camilla from a different carriage.
Charles, 75, disclosed his cancer a month before Kate, and has recently eased back into public duties, including attending commemorations last week for the 80th anniversary of D-Day.
Kate, Charles and the family will watch the ceremony from a building overlooking Horse Guards Parade, a ceremonial parade ground in central London.
When the royal carriages finally came to a stop Louis was the first to leave, followed by his elder brother George and sister Charlotte.
Finally, Kate stepped down wearing a Jenny Packham dress, hat by Philip Treacy and the Irish Guards Regimental Brooch, as she is the regiment’s Colonel.
Kate announced on Friday that she would attend the King’s Birthday Parade after making “good progress” in her treatment.
“I am making good progress, but as anyone going through chemotherapy will know, there are good days and bad days,” Kate said in a statement, adding that she faces “a few more months” of treatment.
Admitting that she is “not out of the woods yet”, the Princess said she has returned to light duties and helping her three children with their schoolwork when she feels well enough.
Support from the public has made a deep impression on the princess, who said she had been “blown away” by the “kind messages” that had made a “world of difference to William and me and has helped us both through some of the harder times”.
Though the King’s birthday is in November, the monarch marks it on the second Saturday of June, as did his mother, the late Queen Elizabeth II.
Since 10.30am, spectators have been treated to a display of pomp and precision involving more than 1,000 soldiers, 250 military musicians and more than 200 horses.
Among the equine participants in the ceremony include Trojan, Tennyson, and Vanquish, three of the five military horses who sparked mayhem in April when they bolted and ran loose through central London.
Additional reporting by PA
