Princess Kate commented on her absence from public life for the first time since announcing her cancer, in a letter to a British army regiment.

King Charles III’s birthday parade, Trooping the Colour, is due to take place in London next Saturday, June 15, and the British Army today conducted a rehearsal, known as the Colonel’s Review.

The Princess of Wales was originally slated to play a key role in the event but pulled out as she continues chemotherapy for cancer.

So she wrote a letter—signed off “Colonel Catherine”—in which she apologized for missing the occasion and praised the troops for their work preparing, while Kensington Palace said she is continuing her recovery at home.

In the letter, Kate wrote: “I wanted to write to you to let you know how proud I am of the entire regiment ahead of the Colonel’s Review and Trooping the Colour.

“I appreciate everyone at Trooping the Colour this year has been practising for months and dedicating many hours to ensure their uniforms and drill are immaculate.

“Being your colonel remains an honour and I am very sorry that I’m unable to make the salute at this year’s Colonel’s Review.

“Please pass on my apologies to the whole regiment. I do hope that I’m able to represent you all once again very soon. Please send my very best wishes and good luck to all involved.”

Kate was diagnosed with cancer after undergoing abdominal surgery on January 16 and began chemotherapy in late February.

Her last public appearance was on Christmas Day though she also recorded a video message in which she announced her cancer on March 22.

Since then, she has signed off a couple of posts with her initial, C, on her and Prince William’s official Twitter account but otherwise not been seen nor heard from as she focuses on getting healthy with peace and privacy at home.

Kensington Palace announced she would miss the Colonel’s Review last week but is yet to comment on whether the princess will make Trooping the Colour on Saturday, June 15.

If she was to appear on the Buckingham Palace balcony, even briefly, it would be a dramatic way to make her first public appearance in more than six months and would likely kick conspiracy theories into the long grass.

It is also not yet clear whether her children, Prince George, Princess Charlotte and Prince Louis, will attend without her, since Prince William will be on horseback, taking part in the parade.

In her March 22 announcement, Kate said: “We hope that you will understand that, as a family, we now need some time, space and privacy while I complete my treatment.

“My work has always brought me a deep sense of joy and I look forward to being back when I am able, but for now I must focus on making a full recovery.”

The palace said at the time that she would return to work only after being cleared by her doctors and they reaffirmed in May that she had not yet been given the green light.