The King has spoken about losing his sense of taste as he discussed the side effects of cancer treatment.
During a visit in Hampshire, he made the remark as he spoke to a veteran who had previously undergone chemotherapy for testicular cancer.
The monarch is receiving treatment for an undisclosed form of cancer and was given permission by his doctors to return to public duties last month.
Ahead of his first major investiture on Tuesday since his cancer diagnosis, the King officially handed over the role of colonel-in-chief of the Army Air Corps to Prince William today.
The monarch and the heir-to-the-throne were pictured smiling while chatting together during a visit to the Army Aviation Centre in Middle Wallop, Hampshire, on Monday.
It came as Kensington Palace posted two photos of the Prince of Wales during previous visits to the Army Air Corps.
"Time flies! Looking back at the last two visits to @ArmyAirCorps in 1999 and 2008 ahead of today's handover at Middle Wallop," the post on X said.
The Army Air Corps is the Duke of Sussex's old unit, in which he served as an Apache helicopter commander and co-pilot gunner during his second tour to Afghanistan in 2012.
The decision to hand the role to William, who served as a helicopter pilot with the RAF, was seen as a blow to Harry when it was announced last year.
The King admitted the handover was "tinged with great sadness" - but hoped the Army Air Corps would continue to go from "strength to strength".
He said: "Let me just say what a great joy it is to be with you even briefly on this occasion but also it is tinged with great sadness after 32 years of knowing you all, admiring your many activities and achievements through the time that I've been lucky enough to be colonel-in-chief of the Army Air Corps.
"I do hope you'll go from strength to strength in the future with the Prince of Wales as your new colonel-in-chief.
"The great thing is he's a very good pilot indeed - so that's encouraging."
The King also unveiled a plaque commemorating an Apache AH Mk1 going on display, the first of its kind to be installed at a UK museum.
William will embark on his first engagement with the Army Air Corps on Monday afternoon, receiving a briefing on its work and inspecting training and operational aircraft.
After speaking to soldiers, he will then leave the base in an Apache as part of a capability flight.
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On Tuesday, the King will knight the Archbishop of Canterbury for his key role in the coronation, and bestow a damehood on bestselling author Jilly Cooper.
The monarch will greet 52 recipients in total, one by one, at Windsor Castle.
The King has invested a handful of people with honours over the past few months.
However, these ceremonies took place in private during individual audiences at royal residences.
(c) Sky News 2024: King Charles tells of losing sense of taste as he discusses cancer treatment side effects
