Prince William expressed gratitude for the outpouring of sympathy for his family following King Charles' cancer diagnosis.

The Prince of Wales was joined by Tom Cruise, a longtime friend of the monarchy, at London's Air Ambulance Charity, where Prince William said he "really appreciates everyone's kindness" following King Charles' diagnosis.

King Charles III was diagnosed with a form of cancer and is undergoing treatment, Buckingham Palace announced Monday.

KING CHARLES DIAGNOSED WITH CANCER, BUCKINGHAM PALACE SAYS

Prince William and Tom Cruise wear matching tuxedos

Tom Cruise, left, and Prince William attend London's Air Ambulance Charity event. (Daniel Leal)

In March 2020, Prince William became Patron of London’s Air Ambulance Charity after supporting their 30th Anniversary Campaign. William previously worked as an air ambulance pilot for the East Anglia Air Ambulance from 2015-17.

The Prince and Princess of Wales joked about their famous friend dropping in at the charitable event with a post shared on X, formerly Twitter: "Fancy seeing you here, @TomCruise!"

PRINCE WILLIAM RETURNS TO WORK WITHOUT KATE MIDDLETON AFTER PALACE SLAMS REPORT SHE WAS IN ‘INDUCED COMA’

In another post, they wrote, "Celebrating the heroes of the @LDNairamb. Their speed, expertise and unwavering dedication makes the city safer."

Earlier in the morning, the Prince of Wales returned to work for the first time since his father's cancer diagnosis was revealed. It was also the first royal appearance for Prince William since his wife Kate Middleton's planned abdominal surgery.

Tom Cruise and Prince William laugh before charity dinner in London

Cruise was on hand to support London's Air Ambulance Charity Gala. (Daniel Leal)

William hosted an investiture ceremony at Windsor Castle, which acknowledged exceptional achievements through six orders of chivalry, and two orders of merit. Recipients are made officers of the Most Excellent Order of the British Empire or officer of the Order of the British Empire.

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Patricia Spruce, a nurse who was awarded an MBE, shared her experiences from the event, which included a conversation with the Prince of Wales.

"Prince William said that Katherine had two Filipino nurses looking after her and they were amazing and kind," Spruce wrote on LinkedIn.

On Monday, Buckingham Palace confirmed a "separate issue of concern" was identified during King Charles' recent "benign prostate enlargement" procedure at the London Clinic. "Subsequent diagnostic tests have identified a form of cancer," the palace said in a statement.

Prince William wears navy uniform at royal ceremony

Prince William returned to royal duties Wednesday following Kate Middleton's hospitalization for abdominal surgery and King Charles' cancer diagnosis.  (Yui Mok)

King Charles was "advised by doctors to postpone public-facing duties" while undergoing a series of "regular treatments," a statement from the palace said. It's unclear what cancer diagnosis His Majesty received.

In addition to Prince Harry and Prince William, the monarch reportedly advised his siblings — Prince Andrew, Princess Anne and Prince Edward — about his diagnosis prior to the public revelation, according to People magazine. 

The Duke of Sussex flew into town from California to visit his father on Tuesday, and left the country the following day.

One day prior to announcing his cancer diagnosis, the king made his first public appearance since receiving treatment for an enlarged prostate. The British monarch waved to well-wishers outside of St. Mary Magdalene Church near Sandringham with his wife, Queen Camilla.

King Charles waving next to Queen Camilla and a priest

King Charles III and Queen Camilla were accompanied by The Reverend Canon Dr Paul Williams at the Church of St Mary Magdalene on the Sandringham estate for Sunday services.  (Max Mumby)

On Jan. 17, King Charles III was scheduled to have a "corrective procedure" for his enlarged prostate. The palace later announced that the surgery had been a success. "His Majesty is doing quite well," a royal source told Fox News Digital.

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Last week, Kate returned home after a nearly two-week stay in a hospital for abdominal surgery.

Kensington Palace shared the news in a statement obtained by Fox News Digital, adding that the Princess of Wales is "making good progress."

Kate Middleton smiles wearing a blue suit

Kate Middleton was hospitalized last month for a planned abdominal surgery. (Samir Hussein)

"The Prince and Princess wish to say a huge thank you to the entire team at The London Clinic, especially the dedicated nursing staff, for the care they have provided," the statement read. "The Wales family continues to be grateful for the well wishes they have received from around the world."

On the recommendation of her doctors, the princess will not resume her public duties until Easter, palace officials said. 

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