In a long and varied diplomatic career, he is likely never to have had a similar experience. Sir David Manning, a former ambassador to Washington and a foreign policy adviser to Tony Blair, found himself clutching a large, cuddly, stuffed pig.
The children's toy had been given to Prince William on a walkabout in Slave Lake, home to a Canadian community recovering from wildfires that devastated their town two months ago.
Sir David, one of William's advisers, was on hand to act as the male equivalent of a lady-in-waiting because the Duke and Duchess of Cambridge had travelled across North America with, in royal terms, a relatively small staff of seven people.
When the Duchess of Cornwall was similarly "launched" abroad in 2005, the entourage accompanying her and the next monarch numbered 16 and included a hairdresser, make-up artist and dresser for William's stepmother.
The prince's desire to travel for 11 days with a close-knit team is yet another example of his cautious, tiptoeing approach to a future he cannot avoid.
Crucially though, he now has someone by his side to help him with this enterprise.
So, how did it go? The response of the press, the pundits and the supporters out on the streets of both Canada and America, was overwhelmingly positive. There were few, if any, critical voices. But it is, of course, early days and the couple can exploit a palpable amount of global goodwill.
It has been striking how a man who will one day appear on the banknotes of at least one country does not always enjoy the limelight.
When a crowd of 300,000 on Parliament Hill in Ottawa for Canada Day gave the couple a sustained cheer, William blushed and looked uncomfortable.
Kate patted his knee. More than once she gave the impression of being the seasoned member of the Windsor clan and he had the appearance of the nervous newcomer.
Overall, they appeared, in public at least, to have had a very good time. Only they know their private assessment of their nearly two-week road trip.
The lesson of history is these first royal tours can be arduous, even after taking into account the fact you are whisked everywhere and do not have to worry about what to cook for tea.
The Duchess of York wrote in her autobiography about her trip to Canada in 1987: "No-one knew how much strain I had endured along the way."
And Diana, Princess of Wales, told the author Andrew Morton that four years earlier in Australia and New Zealand she had cried her eyes out with nervous exhaustion behind closed doors.
Wherever they have gone, William and Kate, who are tactile when together - and with others, especially children - have not been able to escape being spoken about as if they were film stars.
One Canadian radio presenter told his listeners the Cambridges were "mega-celebrities, like Gaga without the meat dress".
It is a comparison - the one to celebrity rather than to Lady Gaga - that may trouble some in royal circles. Most people in the public spotlight have a limited shelf-life. William and Kate are representatives of an institution meant to go on and on.
Despite this potentially niggling worry, the Palace will view Kate's first trip abroad as a success. With her husband, she is presenting a fresh face for an ancient institution.
Prince of Wales
But, of course, that freshness may have reduced a little by the time William eventually inherits the throne. He's in a queue.
It is noticeable how in the coverage of royals in recent months much has been said about the Queen, the Duke of Edinburgh and the Cambridges and rather less about the Prince of Wales.
He was overshadowed by his first wife in the 1980s and did not enjoy the experience. How is he coping, and how will he continue to cope with the focus on his son and his daughter-in-law? In the coming years it will increase, not diminish.
For now though, the duke and the duchess intend to disappear from view. In the coming months, it will very much be a case of now you see them, now you don't.
Prince William will continue to exploit the latitude provided to him by being second-in-line to the throne. It will be only when he finishes his work as an RAF search-and-rescue pilot in probably a year or two, that life as a full-time royal will beckon.
He is returning to his job. She is, once again, an officer's wife who is cautiously - that word again - looking for charitable causes to endorse.
For the former Kate Middleton - who only last year was working for her parents' mail-order company - the tour of Canada and the USA was a significant milestone in her new life as a royal.