Kate Middleton shares 'apologies' for missing Trooping the Color event

Kate Middleton has shared her apology for missing a major rehearsal for Trooping the Color, King Charles' birthday parade, as she continues to stay out of the spotlight despite her cancer diagnosis.

The Irish Guards shared a letter from the Princess of Wales, 42, in a post on colonel's troop. the colour.”

“I appreciate that everyone participating this year has been training for months and putting in many hours to ensure their uniforms and drills are impeccable,” Princess Kate added in the letter.

She continued: “Being your Colonel remains a great honor and I am truly sorry that I will not be able to receive the salute at this year’s Colonel’s Review. Please pass on my apologies to the entire regiment, but I hope to be able to represent again very soon. Please send best wishes and good luck to everyone involved.

The Princess of Wales concluded the letter by writing “Quis Separabit” and signing “Colonel Catherine”.

“The Irish Guards were deeply touched to receive a letter this morning from our Colonel, Her Royal Highness, Princess of Wales. We continue to wish Her Royal Highness a speedy recovery and send her our best wishes. Quis Separabit @KensingtonRoyal @ ArmyInLondon,” the Irish Guards wrote alongside images of the letter.

Kate is the honorary colonel of the Irish Guards, who are leading the charge at this year's celebrations (only one flag can be presented at a time, so all five regiments of the Foot Guards — Grenadier, Coldstream, Scots, Irish and Welsh — rotate at who holds this honor each year). Princess Kate would normally have received the salute at the Colonel's Review for the Irish Guards – which took place on June 8, a week before the grand parade in London – but the palace announced on May 30 that she would not perform not this moment.

Lieutenant General James Bucknall, former commander of the Allied Rapid Reaction Corps who has attended every Trooping the Color since 2009, when he was appointed colonel of the Coldstream Guards, instead took the salute at the event on 8 June.

Last year it was Prince William who led the rehearsal of Trooping the Color as the Welsh Guards regiment, of which he is honorary colonel, took their turn.

Princess Kate has remained out of the public eye since announcing on March 22 that she had cancer and was undergoing chemotherapy. However, she was recently spotted with her family and running errands solo, sources tell PEOPLE.

Prince William, 41, said last month that his wife is “doing well”, although palace sources say she is not expected to return to work until her medical team gives her the all-clear.

It remains unclear whether Princess Kate will join members of the royal family in celebrating the King's birthday on June 15. She has attended the must-see event on the royal calendar every year since her marriage to Prince William in 2011, with the exception of 2020 and 2021 when the event took place. has been reduced due to the COVID-19 pandemic.

The Colonel's Review isn't the first time Kate has missed a major event with the Irish Guards this year. In March, before her cancer diagnosis was revealed and while she was recovering from abdominal surgery in January, she did not attend their traditional St. Patrick's Day parade. Despite her absence, the Irish Guards kept the Princess of Wales in mind during the festivities. A source told PEOPLE ahead of the event that they planned to greet Kate at the end of their fashion show.

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Meanwhile, King Charles is set to attend Trooping the Color on June 15, with a slight change from last year. Although the monarch, 75, has already appeared on horseback in the procession, he will ride in a carriage alongside Queen Camilla.

The king recently resumed a fuller schedule of royal functions, including public outings, as part of his cancer treatment, revealed in February.

Although the royal joked during a May 9 outing to the Royal School of Military Engineering that he was happy to be “out of my cage” after spending several months working mostly behind the scenes , royal outings were reduced after British Prime Minister Rishi Sunak announced on May 22 that a general election would be held in July. Buckingham Palace said the royal family would postpone engagements “which could appear to distract or distract from the election campaign”. However, it was determined that Trooping the Color would go ahead as planned.