LONDON (AP) — Prince William returned to royal duties Wednesday for the first time since his father, King Charles III, announced his cancer diagnosis and his wife Kate was hospitalized for abdominal surgery.

William performed an investiture ceremony at Windsor Castle and is attending a fundraising dinner for London’s Air Ambulance Charity on Wednesday evening.

The 41-year-old heir to the throne temporarily stepped away from public duties last month to help care for Kate and their children following her operation for an undisclosed condition. The Princess of Wales, formerly Kate Middleton, isn’t expected to resume public duties until April.

But Charles’ cancer diagnosis earlier this week is putting extra pressure on the royal family, with the king suspending his own public appearances to focus on treatment and recovery. While receiving treatment for an unspecified form of cancer, Charles will continue with behind-the-scenes work such as reviewing and signing state papers.

“His absence is putting a lot of pressure on the other members of the royal family, who are certainly up to it,” said Sally Bedell Smith, author of “Prince Charles: The Passions and Paradoxes of an Improbable Life.” “And having one of the great stars of the royal family, the Princess of Wales, in recuperation from a surgery” magnifies those strains.

Charles’ illness comes at an awkward time for the House of Windsor.

The king, who ascended the throne just 17 months ago, has pledged to reduce the cost of the monarchy, in part by keeping a lid on the number of “working royals” whose public duties are supported by taxpayer funds.

But with two of the most visible family members out sick, it will be more challenging for the family to keep up.

In addition to the widely publicized pomp and ceremony of royal processions and state visits, the Windsors attend hundreds of little known events every year to recognize the accomplishments of average people and mark local events such as the opening of libraries and community centers. Hundreds of charities cherish royal appearances, which give their good works visibility and credibility among potential donors.

The 75-year-old king was seen in public for the first time since his cancer diagnosis on Tuesday, when he left his offices at Clarence House after a brief reunion with his younger son, Prince Harry.

Harry arrived in London from California less than 24 hours after Buckingham Palace announced the king’s cancer diagnosis. The meeting has raised hopes that the pair can repair their troubled relationship after Harry publicly criticized the royal family for unconscious racism and complained about the way his American biracial wife, former actor Meghan Markle, was treated by palace officials.

Harry and Meghan, once seen as stars of the royal family who could help the Windsors connect with a younger generation, walked away from royal duties in 2020 and now live in California.