The King gave a warm welcome to Canadian Prime Minister Justin Trudeau as he greeted him at Sandringham after being hailed for showing solidarity to Ukrainian President Volodymyr Zelensky.
Charles appeared to give a hearty laugh as the Canadian leader gestured towards him with a pointed figure and shook the monarch’s hand.
Mr Trudeau also clasped the King’s hand in both of his in a demonstration of the ease of their relationship as the pair met in the saloon at Sandringham House.
The private audience on Monday morning came after the monarch welcomed Mr Zelensky to his private Norfolk estate on Sunday in the wake of the president’s dramatic Oval Office clash with US President Donald Trump.
Diplomatic efforts on Ukraine have intensified as Prime Minister Sir Keir Starmer warned Europe’s leaders they stand at a “crossroads in history” and urged them to join his “coalition of the willing”.
Charles, who has invited Mr Trump to pay an unprecedented second state visit to the UK, is increasingly being seen as a unifying figure despite the turmoil on the world’s political stage, through the royal family’s so-called “soft power” diplomacy.
The King and Mr Trudeau were shown sitting side by side in comfy patterned armchairs in the room, which was brimming with furnishings and photographs.
Between them was a small wooden antique table, with a large lamp and a dish filled with potpourri.
In the background was a grand wooden desk, home to a large green plant with small delicate pink flowers, and to the side a grand piano adorned with black and white family portraits.
Sandringham House has been the private home for five generations of British monarchs for more than 160 years and now belongs to the King.
Charles and Mr Trudeau posed for photographs at the start of their private audience.
Mr Trump has repeatedly threatened to make neighbouring Canada the 51st state of the America, claiming that without a massive subsidy from the US it “ceases to exist as a viable country”.
Mr Trudeau, who flew to London to join an emergency defence summit of European leaders at the weekend, said he would raise his concerns on the matter with Charles, who is King of Canada.
The Canadian leader said in London on Sunday that he would discuss matters of importance to Canadians with the monarch and that “nothing seems more important to Canadians right now than standing up for our sovereignty and our independence as a nation”.
Mr Trump has also vowed to impose tariffs on imported goods from Canada as soon as Tuesday amid his concerns over border crossings.
The King has faced criticism for being silent about Mr Trump’s suggestion of annexing Canada.
Former Alberta premier Jason Kenney said “for Canadians disappointed that King Charles has not commented” on Mr Trump’s threats, he can only act on the advice of Canada’s prime minister.
“The Government of Canada should ask the Head of State to underscore Canadian sovereignty,” Mr Kenney posted on X.
Artur Wilczynski, a former Canadian public servant, posted on X: “Canadians will need to decide what purpose King Charles III serves as King of Canada if he can’t even speak up for our sovereignty.”
