The Prince of Wales said the royal family appreciates the “kind messages” they have received after King Charles's cancer diagnosis.
Arriving at a gala dinner for London’s Air Ambulance on Wednesday evening, Prince William waved to people gathered outside the venue in central London.
“We really appreciate everyone’s kind messages, thank you," he said.
Prince William gave his pre-dinner speech at the event, raising funds for London’s Air Ambulance Charity’s new fleet of helicopters, where guests included Hollywood star Tom Cruise and Arsenal football club manager Mikel Arteta.
“I’d like to take this opportunity to say thank you, also, for the kind messages of support for Catherine and for my father, especially in recent days. It means a great deal to us all," the prince said.
“It’s fair to say the past few weeks have had a rather medical focus, so I thought I’d come to an air ambulance function to get away from it all.”
His wife, Kate, Princess of Wales, underwent major abdominal surgery and was released from hospital at the end of last month.
At a reception before the dinner, Prince William, a former air ambulance helicopter pilot, met crews from London’s service and chatted to Cruise and the latest line-up of the 1970s disco group, Sister Sledge.
Public shows support for King Charles outside Buckingham Palace - video
Public shows support for King Charles outside Buckingham Palace
Prince William joked about a pair of custom slippers he wore at the Top Gun: Maverick film premiere, telling the actor, who starred in the sequel: “I haven’t got my Top Gun slippers on."
Cruise responded: “I miss them.”
The gala dinner is raising funds for London’s Air Ambulance Charity’s Up Against Time appeal, which is seeking £15 million [$19 million] to replace the service’s helicopter fleet by the autumn.
Prince William is a former air ambulance pilot with the East Anglian Air Ambulance and during the event will meet crew members, former patients and supporters before delivering a short speech.
London’s Air Ambulance Charity was established in 1989 after a growing consensus of opinion that victims of serious accidents were dying because of the delay in expert medical help reaching them and the time it took to transport patients to hospital.
The service pioneered the doctor-on-board model for air ambulances and aims to bring the hospital emergency department to the scene of an incident.
The Prince of Wales returned to public duties on Wednesday, two days after it was announced that the king is undergoing treatment for cancer.
Prince William carried out an investiture at Windsor Castle, in southern England, which is one of his regular duties.
He presented more than 50 honours during the late morning ceremony, accidentally dropping an MBE medal he was giving to charity worker Suzanne Hutchinson.
The prince quickly picked it up and pinned it to Ms Hutchinson, who was recognised for her services to children with congenital heart disease.
He was returning to official engagements three weeks after taking time off following Kate's admission to hospital for the planned surgery.
