William’s words of praise, delivered during a fundraising gala dinner, also recognised those who wished the Princess of Wales well, as she recovers from planned abdominal surgery.
He told the guests “It means a great deal to us all.”
William had taken time off to support his family after Kate’s operation on 16 January, and returned to public duties once her care and recovery had settled.
But his first day back on duty came as the royal family was dealing with the health scare surrounding his father, the head of state whose reign will pass the 17-month mark on Thursday.
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.
The prince said: “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.
“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.”
When William first arrived at Raffles London, a luxury hotel in Westminster, a member of the press called out some words of support and the prince acknowledged them with a wave and replied: “We really appreciate everyone’s kind messages, thank you.”
At a reception before the dinner, 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.
After guests had taken their seats in the banqueting room they applauded after host and broadcaster Tania Bryer said: “We would like to extend our best wishes to His Majesty the King.”
The gala dinner is raising funds for London’s Air Ambulance Charity’s Up Against Time appeal, which is seeking £15m to replace the service’s helicopter fleet by the autumn.
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 following 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.