So, for the first time in more than a decade, the Prince of Wales is off to America. In 1985 he went with Diana and their host was President Reagan. In 2005, Duchess Camilla will be at his side, with President Bush ready to receive them at the White House.

Clarence House seems proud that George W will be giving the Cornwalls lunch and dinner, attracted no doubt to the global profile it will give the couple. And the prince’s good causes will benefit from some dollars as he shakes hands and dines with America’s super-rich elite. But is that all this trip is — a PR stunt and a fundraiser — or could it have a more serious purpose? The desire, of course, is that once elevated to the world stage Camilla will return from America looking more like our future queen.

The trip is also an opportunity for Charles to gain kudos in his working life. The couple will meet Kofi Annan, visit ground zero, an inner-city school in Washington and organic farms in San Francisco.

In an interview to be broadcast on American television this evening, Charles has said that “I try (to make a difference). I only hope that when I’m dead and gone they might appreciate it a little bit more.” Moaning aside, if this trip goes smoothly there’s a possibility that people might appreciate it sooner than that.

However, given the nature of such visits (royals out of hiding and under intense and prolonged public scrutiny) the potential for gaffes is all around. For every Diana dance with John Travolta, remember Prince Philip on a state visit to China in 1986 telling English students: “If you stay here much longer you’ll all be slitty-eyed.”

It should be easier to keep out of trouble in the Bush White House, reportedly a more staid destination than it was in the Reagan years. Given his slump in popularity, the US president, a teetotaller who is said to retire at 9pm, won’t be ungrateful for the pizzazz of a royal visit though. But I wonder if the “special relationship” with the United States is really helped by such an expensive exercise? Prince Charles is a curious ambassador for our country. In my time with him, there must have been at least three serious attempts to persuade him to visit the United States. Yet he was always nervous of America — fearing rejection by a culture that he saw as being more aligned to the Princess of Wales’s celebrity than his man-with-a-mission message.

He was wrong, of course. If you forget the strange world that is Washington, the market in America for his theories on farming, medicine and the environment is more receptive than in Britain. Indeed, much of the work of his Prince’s Trust and Business in the Community was pioneered in America and transplanted to the UK by the folk who run these two charities. But still he had an absolute mental block on visiting.

Tens of thousands of pounds were spent sending us there to research opinion and opportunities for links between him and America. We started diverting funds from his American foundation (which had been set up to funnel cash from America to the UK) to good causes in New York and Washington.

He fought against this at every turn, but we did it anyway — knowing the good it would do and the benefits he would reap in time. We even hired a PR firm in New York to help promote the prince there at the time of his 50th birthday. Upmarket focus groups were held (one chaired by Barbara Walters, the television presenter) to help us gauge opinion among America’s elite.

We found a residual warmth towards him; a feeling that he was too concerned with fundraising in America — a criticism levelled at all members of the royal family except the Queen. And a belief that he should stop hiding Camilla in the shadows and move on with his life.

Indeed, much of the drive to bring Camilla into the open was fuelled by the encouragement we received in America. That’s why her debuts with Charles were at dinners for his American supporters in London — the first time they went out to a semi-public engagement together, their first charity dinner at Buckingham Palace and even a few weeks ago, their first event at Balmoral Castle.

Charles still wouldn’t budge and go to the States himself. Instead, he decided that Camilla should go on her own to “test the temperature”. His feeling was that if she came out of New York unscathed, then perhaps the tide really was turning.

Accepting an invitation from a friend, Camilla jetted off to New York on Concorde to be greeted by headlines claiming it was her first “royal tour”. I suppose it was, in a way, and it certainly had the effect of jolting public opinion a few more steps along the way to accepting her as a legitimate royal consort.