Prince Harry steps out solo in London while King Charles III attends Buckingham Palace garden party

Prince Harry, the Duke of Sussex, is not seeing his father King Charles III while he is in London to mark the 10th anniversary of the Invictus Games, ABC News has confirmed.

A spokesperson for the duke told ABC News on Tuesday that Charles' schedule does not allow time for him to see his younger son, who now lives in the United States.

"It unfortunately will not be possible due to His Majesty's full programme," the spokesperson said of a meeting between Harry and Charles. "The Duke of course is understanding of his father's diary of commitments and various other priorities and hopes to see him soon."

Harry attended a service for the Invictus Games' anniversary solo on Wednesday at St. Paul's Cathedral in London. He founded the Paralympic-style competition for wounded service members in 2014.

Though no members of Harry's immediate family joined him at the ceremony, it was attended by relatives of Harry's mother, the late Princess Diana.

On the same day that Harry attended the service, his older brother Prince William led an investiture ceremony at Windsor Castle.

Elsewhere on Wednesday, Charles held his weekly audience with British Prime Minister Rishi Sunak and then made a surprise appearance at the first Buckingham Palace garden party of the season.

Joining Charles at the palace were his wife Queen Camilla and other royal family members including Princess Anne; Prince Edward and his wife Sophie, the Duchess of Edinburgh; and the Duke and Duchess of Gloucester.

The last time Harry and Charles saw each other was in February, when Harry flew to London to visit Charles after the palace publicly shared that Charles had been diagnosed with an undisclosed type of cancer.

Harry reportedly met with Charles, who has since begun cancer treatment, for less than an hour on Feb. 6, and stayed overnight in a hotel before departing the next day from London's Heathrow Airport.

In an interview with ABC News' Will Reeve just after his visit, Harry said he hoped to see Charles again soon, saying, "I've got other trips planned that will take me through the U.K., or back to the U.K., and so I'll stop in and see my family as much as I can."

While visiting with Charles, Harry did not see William. It is not known whether the brothers, who have a strained relationship, will see each other while Harry is in London this week.

A spokesperson for both Buckingham and Kensington Palaces declined to comment to ABC News.

Prior to February, Harry had not seen his 75-year-old father since the king's coronation last May at Westminster Abbey.

As he did in both February and May, Harry traveled to London this week solo, visiting his hometown without his wife Meghan, the Duchess of Sussex, or their two children Archie and Lilibet.

Following his visit to London, Harry will travel to Nigeria, where he will be joined by Meghan.

The Sussexes are visiting the African country on invitation from the country's highest-ranking military official, its Chief of Defense Staff.