Kate Middleton apologizes for missing Trooping the Colour rehearsal

Originally appeared on E! Online

A rare message from Kate Middleton has been made public as she continues her cancer treatment.

In a letter to the British Army's Irish Guards regiment, the Princess of Wales expressed regret for missing the Colonel's Review, a rehearsal of the annual Trooping the Colour parade in honor of King Charles III's birthday. The preliminary event would have seen Kate, 42, take the salute as the unit's honorary Colonel for the first time.

"I wanted to write and let you know how proud I am of the entire Regiment ahead of the Colonel's Review and Trooping the Colour," read the letter, posted on the Irish Guards' X page. "I appreciate everyone trooping this year has been practicing for months, and dedicating many hours to ensuring their uniforms and drill are immaculate."

The message continued, "Being your Colonel remains a great honour, and I am very sorry that I'm unable to take the salute at this year's Colonel's Review. Please pass my apologies to the whole Regiment, however I do hope that I am able to represent you all once again very soon. Please send my very best wishes and good luck to all involved."

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The letter ended with the words, "Quis Separabit," which means "who shall separate (us)," and was signed, "Colonel Catherine."

Members of the regiment broke out in applause after the letter was read to them, as seen in a video shared on its X page.

"The Irish Guards were deeply touched to receive a letter from our Colonel, Her Royal Highness, The Princess of Wales this morning," read a message shared on the account. "We continue to wish Her Royal Highness well in her recovery and send Her our very best wishes. Quis Separabit."

Kate's absence from the rehearsal had been announced last month. "This year General James Bucknall K.C.B., C.V.O will carry out the role of Inspecting Officer," a Kensington Palace spokesperson told NBC News May 30. "On behalf of HRH The Princess of Wales at Colonel's Review as she continues her recovery."

Kensington Palace has not commented on whether Kate, who has kept away from the spotlight since revealing her cancer diagnosis in a video released in March and last attended a public event last December, will make an appearance at the main Trooping the Colour event June 15.

In past years, the princess, her husband Prince William and their three kids Prince George, 10, Princess Charlotte, 9, and Prince Louis, 6, have traditionally joined other royal family members to make a public appearance on a Buckingham Palace balcony during the annual parade.

The Prince of Wales recently shared a health update about his wife. Speaking to veterans at the 80th anniversary of the D-Day Landings in Portsmouth June 5, William said Kate was getting better and added, "She'd have loved to be here today."

Trooping the Colour celebrates the U.K. monarch's birthday every spring. The King, who turned 75 last November, is also battling cancer and has confirmed his attendance at the parade. However, he is expected to travel by carriage instead of horseback, multiple outlets have reported.