Prime Minister Justin Trudeau passed through the pomp at Buckingham Palace to have his first audience with the Queen – as Prime Minister.
When they came face to face, they spoke about how they had met before – as a child, he met the monarch when his father, Pierre Trudeau, was prime minister.
"Very nice to see you again," the Queen said to the Prime Minister. "In rather different circumstances."
Mr. Trudeau alluded to the fact he was a child on the previous occasion: "I will say you were much taller than me the last time we met."
"It's extraordinary to think of," the Queen replied. "Now you are having a very busy time."
The noon-hour visit to Buckingham Palace was Mr. Trudeau's first royal experience as a true participant.
Two of his own children, Ella-Grace and Hadrien, along with his wife, Sophie Grégoire-Trudeau, were in the palace but not the private audience. They met the Queen later, aides said.
The meeting had ceremony. While Mr. Trudeau's family and aides sat in an antechamber, the Queen arrived and entered a private room. Then Mr. Trudeau arrived to be formally introduced by the Queen's Equerry with a ceremonial sword. "The Prime Minister of Canada, Your Majesty," he announced.
There was no sign that Mr. Trudeau had any urge to make the kind of rebellious gesture famously made by his father at a reception for G7 leaders in 1977, when Pierre Trudeau did a pirouette behind the monarch.
In fact, Pierre Trudeau was said to have a good relationship with the monarch, over a number of visits – and his son indicated he remembers those times warmly.
Before the meeting, the Prime Minister's spokesman said Mr. Trudeau didn't remember precisely when he last met the Queen – he was between 7 and 12.
"She was always lovely and gracious. She was very tall, which points out how little I was at the time," Mr. Trudeau said in a brief e-mail passed on by his press secretary.
"They were nice moments because I knew how much my dad liked her. You could tell my father was really proud to be introducing his son to the Queen."
This time, however, he is the Queen's Prime Minister, and meeting her is an important formality – if not an actual constitutional necessity. Canadian prime ministers usually try to visit the Queen early in their tenure – former PM Stephen Harper visited her for the first time in July, 2006, five months into his tenure, and several times thereafter.
Canadian prime ministers have nothing like the regular schedule of chats with the sovereign that their British counterparts do; in Canada, the Governor-General performs most of the monarch's constitutional duties. The Queen has held weekly meetings with every British prime minister since Winston Churchill, at least when both are in London. Prime Minister David Cameron has said he appreciates the opportunity to have an hour-long chat on Wednesday evenings – but isn't sure they're as useful to the Queen.