Princess Kate has written to the Irish Guards, the regiment of which she is honorary colonel, to express her regret at missing their final rehearsal before next week's Trooping the Colour ceremony.
The Princess bowed out of the rehearsal event, known as the Colonel's Review, due to her ongoing cancer treatment.
"Being your colonel remains a great honor and I am very sorry that I'm unable to take the salute at this year's Colonel's Review," she wrote in the letter posted on X by the regiment.
"Please pass my apologies to the whole regiment, however I do hope that I am able to represent you all once again very soon, " she wrote.
The Irish Guards are leading this year's Trooping the Colour, the military parade to mark the king's official birthday, and Kate was due to watch the dress rehearsal Saturday.
Kate Middleton: A timeline of her cancer diagnosis, surgery and absence from public duties"I wanted to write and let you know how proud I am of the entire regiment ahead of the Colonel's Review and Trooping of the Colour," Kate began her letter.
"I appreciate everyone trooping this year has been practicing for months, and dedicating many hours to ensuring their uniforms and drill are immaculate," she wrote.
The letter was read out to the regiment who responded with applause.
The Princess of Wales concluded her letter with the regiment's motto, "Quis Separabit," which translates to "Who shall separate us?" She signed it, "Colonel Catherine."
It is still unclear whether the princess will be at next week's Trooping the Colour. Kensington Palace has neither confirmed nor denied her attendance at the event which is a major one on the royal calendar. It marks the king's official birthday and includes a balcony appearance by the family at Buckingham Palace and a fly over by the Royal Air Force.
King Charles, who is also undergoing cancer treatment, has confirmed his attendance. He rode a horse at last year's parade but aides have said he will be in a carriage this year, for health reasons.
"The Irish Guards were deeply touched to receive a letter from our Colonel, Her Royal Highness, The Princess of Wales this morning," the regiment posted on X.
"We continue to wish Her Royal Highness well in her recovery and send Her our very best wishes. Quis Separabit."
In March, the 42-year-old princess revealed in a video message that she had been diagnosed with cancer and had started chemotherapy.
The palace has not disclosed the specific type of cancer or additional details about Kate's treatment.
In her announcement, Kate requested privacy for herself and her family, stating, "We hope that you will understand that, as a family, we now need some time, space, and privacy while I complete my treatment."
The palace also mentioned that Kate would resume her official duties once her medical team gives the clearance.