King's big moment in Canada after Trump row

"This is a big deal for the King to do this," says Jeremy Kinsman, former Canadian high commissioner to the UK, as King Charles prepares for a historic visit showing support for Canada, which is facing pressure from US President Donald Trump.

"I hope that Trump understands," says Mr Kinsman, ahead of the King becoming the first monarch to open Canada's Parliament in almost 70 years.

So what can we expect from his speech as Canada's head of state, to be delivered in French and English in Ottawa on Tuesday?

It will be written on the advice of Canada's government. But along with the workaday lines on policy plans, Mr Kinsman expects a message, loud and clear, that Canada will not be the US 51st state.

"It's going to be very affirmative of Canadian sovereignty. And I can say personally that it's something that King Charles will celebrate saying. I have no doubt," says Mr Kinsman, who worked as a diplomat with the King when he was Prince of Wales.

"It will say the government will protect, pursue and preserve the sovereignty of Canada as an independent state," he predicts about the speech, which follows an election won by Mark Carney on a wave of anti-Trump sentiment.

The King's mother, the late Queen Elizabeth II, was the last monarch to open Canada's Parliament in 1957 and was also the most recent to deliver the "speech from the throne" in 1977, in a ceremony that marks the start of a parliamentary session.

She began that speech with a few of her own personal comments - so there is scope for the King to add his own thoughts.

"I don't know what pronoun they'll use. He'll be talking about the 'government proposes'. But I don't know if they'll throw in an "I". Either way he'll be identified with it," says Mr Kinsman about the personal nature of this speech from the King in Canada - a Commonwealth country and Nato partner.

It's going to be a more dressed-down event than the pomp of the Westminster state opening of Parliament. The King will be in a suit rather than a gown and crown, reading a speech that could last about 25 minutes, much of which will be about the government's legislative plans.

There are also likely to be nods to the importance of Canada's First Nations communities, in a speech that comes on the first visit to Canada from King Charles and Queen Camilla since the start of their reign.

The King, invited by Mr Carney, will have to balance a message of solidarity with Canada, without jeopardising the UK's relationship with the US.

"The King has long experience and great skill in walking that diplomatic tightrope," says a royal source.

"He's held in high regard around the globe and across the political spectrum, with good relations with world leaders who understand his unique position."

Mel Cappe, a former Canadian minister and senior civil servant, has been involved in preparing such speeches from the throne, usually delivered by a governor general.

He expects the King to add a "few paragraphs of his own at the beginning" to "give his own personal view", but the overall text of the speech will be approved by Canada's prime minister and his officials.

"He's not going to poke President Trump in the eye. That would cause a problem for Canada. On the other hand he isn't going to suck up to Donald Trump," says Prof Cappe, who was also a high commissioner to the UK.

He believes this intervention could have a big impact: "Symbolically this is huge. President Trump has a lot of admiration for the monarchy. He is impressed by the royals."

This royal moment will be a platform for Canada's government to talk about tariffs and to mention the visit to the White House where PM Carney said Canada would "never" be for sale, says Prof Cappe.

"So somewhere in that speech, look for the word "never"," he says.

President Trump, as shown in his recent controversial White House meetings with South Africa's President Ramaphosa and Ukraine's President Zelensky, can be an unpredictable diplomatic partner.

"The old alliances are breaking down," says Mr Kinsman. And against a background of such uncertainty, King Charles has been part of an unexpected international balancing act.

He became a key part of the charm offensive to maintain the UK's good relations with President Trump, with an invite for a second state visit. Now he's going with a message of reassurance to the Canadians.

Sir Keir Starmer has been using the King to get closer to Trump, while Mark Carney is using him to keep Trump further away.

"He isn't anybody's tool or fool. This is something that he believes… It genuinely is something that he wants," says Mr Kinsman about the King's support for Canada.

The former diplomat remembers how much the then Prince Charles showed a personal affection for Canada and a sense of duty towards its people. A planned trip last year had to be cancelled because of his cancer diagnosis.

There are many strong links. The throne on which the King will sit to make his speech includes wood from Windsor Great Park - part of the Crown Estate.

Mr Kinsman says that many Canadians have been traumatised and upset by what he calls the "appalling" language of President Trump over wanting to take over Canada. It's shaken their view of the world and the new prime minister will be expected to stand up to the US.

Mr Carney has said that Canadians were not "impressed" by the UK's invitation to President Trump for a state visit. But Mr Kinsman says that's Canadian understatement for being "disgusted" by the invitation. It really rankled.

Nonetheless he says that many Canadians are pragmatic enough to see the UK needs to keep good relations with the US and that the King - who is head of state of both the UK and Canada - has to play both roles in this "strange duality".

That's rejected by Peter Donolo, a director of the Canadian International Council think tank, who believes there is an impossible contradiction in the King being different things for different countries.

"On the one hand they're using Charles in the UK to curry favour with the Americans and then it seems our government wants to use him to stand up for Canada. You can't have it both ways," says Mr Donolo.

He sees the monarchy as "irrelevant" to this dispute with the US. "It won't have any impact on how Trump views Canada," says Mr Donolo.

In theory the King acts in two separate and distinct roles, taking advice from the UK government on UK matters and advice from the Canadian government in Canada. There are differences too. In Canada, the reference to the King as "defender of the faith" was scrapped from his title.

Elizabeth McCallion, who teaches political science at the University of Toronto, thinks many Canadians don't really have much interest in the constitutional complications around the role of the King.

But she says people in Canada were profoundly offended by Trump's aim to annexe their country - and were "disappointed" that they had relatively little backing from the UK, which seemed to be "buddying up to Donald Trump".

They're now watching to see what the King might say to support them.

"People are recognising that this is momentous," she says.