BBC News Royal Correspondent
He was, once, a man alone. At times, the Prince of Wales appeared rather a lonely figure on the international stage.
Camilla's presence has stopped Charles from cutting a lonely figure
Unaccompanied, for more than a decade, he sat through countless state banquets, seminars and welcoming speeches.
All that has now changed - and so has he.
With the Duchess of Cornwall by his side and abroad together for the first time, the Prince appears relaxed and keen to ensure his wife is coping with her new life inside the royal goldfish bowl.
Her presence has obviously increased interest in this visit to the US.
Officially, the talk is of a trip designed to strengthen the already close ties between the two countries.
Unofficially, the focus - especially of the reporters - is on how Camilla is coping.
Royal officials, some hired at great expense to project an image of Prince Charles as a King-in-Waiting, are now devoting time and energy to providing updates on the Duchess' ever-changing wardrobe.
They even know the names of President Bush's dogs - Barney and Miss Beasley - after the royal couple encountered them during their time at the White House.
It was a bold move sending Charles and Camilla to America, just seven months after they got married.
Canada or a European country with a monarchy would have been a safer option.
The States, as everyone knows, has traditionally been regarded as Diana country after the late Princess danced with John Travolta at the White House and transformed the Grease star, according to his own account, 'into a Prince for fifteen minutes'.
But of course, people here, just like in Britain, are not frozen in time.
The Prince's first wife died eight years ago and he has re-married.
For every American you meet who talks of nobody replacing Diana in their affection, there'll be another who is prepared to give this middle-aged couple a chance.
Camilla's learning the royal ropes fast.
The trip has seen Camilla grow into her role as a senior royal
Her brief apprenticeship at home was little preparation though for the intensity of the flash bulbs popping when she swept into a glitzy Manhattan reception or the White House.
There have been some endearing moments.
A fumble with an errant earring may not be regal, but it is human.
When she was walking behind President Bush and his wife she opted for the tarmac rather than the red carpet.
There is no Camilla fever here, but there is interest and that carries with it its own dangers.
Royal officials do not want history to repeat itself.
When Charles was married to Diana, there would be cheers from the sections of the crowd graced with her presence and groans if the Prince was all they got.
He once told one group, "I'm afraid you've got me. You'd better ask for your money back."
So second time round, his wife is more often than not seen working the same section of crowd as her husband, rather than striking out on her own.
This projects an image of Camilla the supporter, not the upstager.
Prince Charles is using this trip to focus on the issues he is passionate about.
His speech at the White House banquet, where he talked of people looking to the US to take a lead on the most crucial issues facing the planet, is being widely interpreted as an attempt to nudge the president to take a stronger line against global warming.
He has delivered a 40-minute speech about architecture and in San Francisco he will focus on the environment and organic farming.
So how is the royal visit being received in a country which a few centuries ago jettisoned the Prince's ancestors?
The brutal truth is that a happily married couple in their 50s does not set editorial pulses racing.
There were some rather rude comments in New York about Camilla's clothes, with one tabloid calling her Frump Tower.
She apparently, and perhaps fortunately, is too busy to read such headlines.
Such acerbic opinions aside, the truth appears to be that Charles and Camilla are, at best, generating curiosity - at worst indifference.
Whatever the public reaction, it cannot mask the fact that this visit is another and perhaps the final step in the transformation of Camilla Parker Bowles into the Duchess of Cornwall - a senior royal at the heart of the royal family.