King Charles met with Canadian Prime Minister Justin Trudeau at Sandringham on Monday morning.
The private audience took place at the monarch's Norfolk estate.
Mr Trudeau flew to London for the meeting following his attendance at an emergency defence summit of European leaders over the weekend.
The Canadian leader is set to return to Canada later on Monday.
King Charles met with Canadian Prime Minister Justin Trudeau at Sandringham on Monday morning.
PA
The summit in London was described as the biggest European peace gathering since the end of the Second World War.
Sir Keir Starmer and other world leaders joined Mr Trudeau at the emergency defence summit.
The Prime Minister warned European leaders they stand at a "crossroads in history" during the talks.
He urged them to join his "coalition of the willing" in diplomatic efforts on Ukraine.
Mr Trudeau flew to London for the meeting following his attendance at an emergency defence summit of European leaders over the weekend.
PA
US President Donald Trump has repeatedly threatened to make Canada the 51st state of America.
He has claimed that without massive US subsidies, Canada "ceases to exist as a viable country".
Trump has also vowed to impose tariffs on imported goods from Canada as early as Tuesday.
These threats have raised significant concerns about Canadian sovereignty.
Mr Trudeau was set to raise his sovereignty concerns with King Charles, who is also the Head of State in Canada.
The Canadian leader said in London on Sunday that he would discuss matters of importance to Canadians with the monarch.
"Nothing seems more important to Canadians right now than standing up for our sovereignty and our independence as a nation," Mr Trudeau stated.
The monarch welcomed Ukrainian President Volodymyr Zelensky to Sandringham just a day before meeting Trudeau.
PA
King Charles is increasingly being seen as a unifying figure despite global political turmoil.
The monarch welcomed Ukrainian President Volodymyr Zelensky to Sandringham just a day before meeting Trudeau.
This diplomatic engagement came after Zelensky's dramatic Oval Office clash with President Trump.