Why Kate Middleton Isn't with the Royals at Japan State Visit Despite Trooping the Colour Appearance

Kate Middleton wasn't on hand to help with hosting duties as Prince William, King Charles, Queen Camilla and more royals welcomed the Emperor and Empress of Japan to the U.K.

Emperor Naruhito and Empress Masako officially kicked off their state visit on June 25. Prince William, 42, greeted the couple at their hotel before heading to Horse Guards Parade in London for the ceremonial welcome with King Charles, 75, and Queen Camilla, 76.

After lunch, a display of items from the Royal Collection and a visit to Westminster Abbey, the Emperor and Empress returned to Buckingham Palace for an evening gala.

Princess Kate's absence on the first day of Japan's state visit was expected. Although the Princess of Wales, 42, stepped back into the spotlight for the first time in nearly six months at Trooping the Colour on June 15, the outing for King Charles' birthday parade did not signal a return to royal work and public life.

Kate said in a personal letter released on June 14 that she is "starting to do a little work from home" and expressed a "hope to join a few public engagements over the summer." However, outings in the coming weeks will depend on when she feels able and medical guidance.

The Princess of Wales said in the message that she is "making good progress, but as anyone going through chemotherapy will know, there are good days and bad days. On those bad days, you feel weak, tired and you have to give in to your body resting. But on the good days, when you feel stronger, you want to make the most of feeling well."

Princess Kate described her treatment as "ongoing" and said it will be for "a few more months."

A source close to the royal household exclusively tells PEOPLE in the latest cover story, "She has been doing what’s right for her and recovering privately at home. She is dealing with it the best she can."

Since her appearance at Trooping the Colour, Princess Kate has remained out of the public eye, skipping events that she usually attends such as Garter Day and Royal Ascot. The royal also appeared to stay home when Prince William celebrated his birthday on June 21 at Taylor Swift's London concert with Prince George and Princess Charlotte, posing for a selfie with the pop star.

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Prince William started the Japanese state visit by welcoming Emperor Naruhito and Empress Masako at their hotel in London on behalf of his father. During the South Korean state visit in November 2023 and the South African state visit in November 2022, Princess Kate joined her husband for the prominent duty.

Kate has also been attending the state banquets, which usually occur on the first evening of a state visit, since 2015. The glamorous dinners in the ballroom of Buckingham Palace call for royal women to sport ball gowns and tiaras, with Queen Mary's Lover's Knot Tiara being the Princess of Wales' go-to headpiece over the years.

Princess Anne was also unable to attend the Japanese state banquet amid her hospitalization due to an accident that occurred on June 23. King Charles' sister, 73, sustained a concussion and minor injuries consistent with a potential impact from a horse's head or legs at her Gatcombe Park home. The Telegraph reports that the Princess Royal is suffering memory loss related to the incident, which is thought to be temporary.

Queen Elizabeth's only daughter will also not be able to make her scheduled visit to Canada this week.

A Buckingham Palace spokesperson said on June 24, "Her Royal Highness sends her apologies to any who may be inconvenienced or disappointed as a result."