Justin Trudeau's first audience with the Queen: what happens, and why

It's a rite of passage for any new Canadian prime minister: the trek to Buckingham Palacefor a formaltte--ttewith the Queen.

And as heembarks on his second world tour injust two weeks,Prime Minister Justin Trudeauwas receivedby Her Majesty today at the royal residence in the heart of central London. She granted him in the parlance of the monarchy an "audience."

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The two hada private conversation, free from themenagerie of politicaladvisersand palace staff that usually accompany the two leaders. And because such proceedings are strictly confidential, it is difficult to know what happened beyond the gilded doors of the royal reception room.

What we do know is that theQueen does not offer political commentaryher position demands nonpartisanship. Rather, she serves as a sort of sounding-board for prime ministers as they grapple with the challenges of governing.

Vernon Bogdanor, a professor ofgovernment at King's College, London, and an adviser onthe Broadway playThe Audience, a fictional depiction of suchmeetings, says the Queen will likely draw on her historicalknowledge to advise the 42-year-old fledgling leader.

"The Queen might well say to the prime minister:'Ameasure similar to the one you are suggesting was proposed around 25 years ago when you were still at university. You probably do not remember, but it did have some bad results. Perhaps you might have a look at what happened and discuss it with your colleagues," Bogdanor says.

Trudeau would not be obligedto accept her advice, but he could file it away for consideration when drafting legislation.

One British prime minister, James Callaghan, characterized an audience with the Queen as something akin to visiting a psychiatrist.

The Queen's longest-serving British prime minister, Margaret Thatcher, wrote in her memoirs that thevisits are much more than a chance to share a pot of tea.

"Anyone who imagines that they [the audiences] are a mere formality or confined to social niceties is quite wrong; they are quietly businesslike and Her Majesty brings to bear a formidable grasp of current issues and breadth of experience," Thatcher wrote.

Justin Trudeau, no stranger to royal family

It's a daunting task for any new prime minister: impress a monarchwho has quite literally met hundreds of heads of state. After all, Trudeau is thetwelfthCanadian prime minister to serve under the Queen since she ascended to the throne in 1953.

"If anybody is going to be on their toes, it's going to be the prime minister," said Robert Finch, the dominion chairman of the Monarchist League of Canada. "She will have done all her homework. Canadian prime ministers have always commented on just how well-informed and knowledgeable the Queen is about Canadian affairs."

The monarchis well briefed by her Canadian secretary, Kevin S. MacLeod, on such matters. And she is also known to poreover cabinet documents, parliamentary papers andreports from ambassadors.

But there was a natural icebreaker for Trudeau: He's already met her, a perk that comes with being the son of a man whowasone of the country's longest-serving prime ministers.

"There were lunch hours where I wouldn't eat at school because we had to rush home to have lunch with the Queen," Trudeaurecounted in an 2013 interview. "At the same time, it was instilled upon us that this was a privilege and a responsibility, and nothing made us better than anyone else maybe randomly luckier."

Pierre Trudeau, the unlikely monarchist

The Queen and Pierre ElliottTrudeau had a relationship complicated by his republican leanings.

As a student, he penned an essay criticizing Canada's relationship with the British Empire as a relic of our colonial past.Later, as prime minister, hewas famously caught on camera doing a pirouette behind the Queen as they took part in a G7 summit in London.

But his attitudes softened with timeas John English, one of Trudeau'sbiographers, recounts in his bookJust Watch Me. Whenfaced with the realities of governing in an erapolarized bytwo superpowers, Trudeaulearned toappreciate the Commonwealth of Nations as a multilateral force for good.

But more than that, his relationship with the Queen warmed considerably, going so far as to say shedid "a first rate job" as head of state, and that he was impressed by her attention to events in Canada.

The Queen was equally smitten, inductingthe one-time republican rebel into the Order of the Companions of Honour, a prestigious club that never has more than 65 members at one time andwho are chosen for their exceptional service to the Commonwealth.

The younger Trudeau, for his part, has said thatthe role of the Queen in Canada will see little change under his leadership.

In announcing the meeting,Trudeau promisedthat "Her Majesty will remain an integral part of our country's progress and future."

And the timing of the meeting may signify that Trudeauhastaken that pledge seriously. Whereas it took Stephen Harper more than half a year after his election to meet the Queen, Trudeau is making the visit after only a month on the job.

"He's made a point to meet the Queen very early in his mandate, it's certainly agood signal," Finch says. "And it's hopefully the first [meeting]of what will be many more to come."