This time, thank goodness, the stranger was harmless and well-washed, and wanted nothing more than to kiss Pippa Middleton on the cheek.

However, the ease with which Erik Smedhs, a male admirer, was able to get close enough to plant a smacker on the future Queen’s sister pointed up many of the challenges and contradictions at the heart of being Pippa Middleton.

Here is a girl who has been shot to fame simply by her association with the Royal Family, becoming an internet phenomenon when her shapely ass became an international superstar at last year’s wedding. She didn't ask for it, but she now generates more interest internationally than her sister Kate. Her sister and brother-in-law rely on her as part of their ‘kitchen cabinet’ of informal advisers and she is at the heart of the leak-free inner circle of trust of the Young Royals.

And yet, she is not, technically or officially a royal. If, as a journalist, you contact the Royal press office to ask a question about Pippa, you are told politely but firmly that Pippa is not part of their remit. But a press office is the least of Pippa’s worries. The real problem is that Pippa has none of the benefits, protection or state funding that her sister does.

Pippa is a private individual and although in the UK, and especially at home in London, she can be given a little extra care and attention by local police forces, essentially, she must fend for herself. Chaotic scenes that came perilously close to descending into media scrums surrounded Pippa every time she stopped for refreshments yesterday. The chaos culminated with a kiss that, had it been directed at Harry, Kate or William, might have resulted in guns being drawn and an arrest.

In his first interview last night, conducted with the Royalist, Mr Smedhs, a 20-year old student and part-time truck driver, who lives at home with his parents in the Swedish town of Lidingo, said there was no security around Pippa when he made his lunge.What did she make of his gesture?‘I think she thought it was funny,’ he said.

Requests for comment to Miss Middleton, sent via her publishers Penguin and her parents website, Party Pieces, where she is employed, went unanswered.

Mr Smedhs said he did not ask Pippa’s permission to kiss her but just ‘grabbed all the courage that I got’ and went for it.

‘I said that we have a tradition here in Mora when you reach the goal and then I kissed her. It actually is a tradition, but just for the winner of the race.’

Mr Smedhs was actually an official with some kissing in his job description at the 56-mile cross-country ski race. As an elite track and field runner, he was invited to be the ‘Kransmas’ or flower man, the official who presents the winner of each class, male and female, with a wreath of foliage at the finish line, and it is indeed customary for the Kransmas to bestow a formal kiss to the winner of the female class. But this official kiss is more like a non-contact French kiss of greeting, a shaking of hands, not the closed-eyes smacker he actually delivered.

Pippa clearly enjoyed the race, and laughed off the incident, but it can’t be particularly pleasant to be accosted by strangers kissing you when you are cold and exhausted at the end of a seven-hour ski marathon, and she hurried away from Mr Smedhs and the finishing area as soon as possible after getting off her skis.

Almost one year on from the royal wedding that made her a star, the Mr Smedhs’s kiss gets to the very heart of all the contradictions surrounding Pippa. How does she intend to use her fame? Does she want to be a star in her own right? And how she will deal with the invasion of privacy that is the price of celebrity?

According to those who know Pippa, the answer to whether or not she wants to be a star appears to be yes. She certainly wants a career as a successful author. Pippa surprised many when she sold a book to Penguin late last year about organizing parties for over half a million dollars. According to sources in the publishing world, she attended all the meetings with publishers herself, and is contractually committed to being involved in the promotion of the book.

No-one, least of all Pippa, is under any illusion that publishers are really interested in this book because the younger Miss Middleton has any special insights into the best ways to decorate cup-cakes or wrap birthday presents. Pippa knows she is selling herself as a brand, and when the book comes out and she starts doing interviews to promote it on the American networks, it will be increasingly hard for her to argue she is a private individual.

Selling the book and marketing brand Pippa is clearly in conflict with her recent complaints about the level to which her privacy has been invaded by dozens of freelance paparazzi camped outside her house. Pippa’s lawyers sent letters to a half-dozen photographic agencies that syndicate the pictures worldwide on behalf of the paparazzi photographers, warning them that their behavior constituted harassment.

The letter described Pippa’s “serious distress and anxiety” and suggested that her lawyers had themselves been collating photographic evidence against the photographers concerned. “It is extremely intimidating to our client to have to face a group of unknown men outside her home and office who pursue her both day and night,” the letter read.

Then there is the question of money. Pippa’s supporters point out that she needs to earn an income still, unlike her sister, and can therefore hardly be blamed for making a lucrative book deal. Some at the palace would prefer it if Pippa would marry a rich aristocrat like George Percy and retire to comfortable obscurity in the English countryside. Alternatively, they argue, she could become a lady-in-waiting to her sister and step inside the protective caress of the Palace.

But that’s unlikely to happen. Pippa is fiercely ambitious. Pippa was not responsible for her initial fame, when her regal ass was flashed around the globe and she stole the show from her sister.

Says Katie Nicholl, royal writer and author of Making of a Royal Romance says: ‘No-one, least of all Pippa herself, could have expected the level of fame that has landed at her feet since the wedding, but Pippa is very clever and very ambitious, and she knows that she has an incredible platform now to make herself into a big star. She is very career driven and she is going to make the most of it.’

But, of course, like many a celebrity before her, Pippa is discovering that when it comes to privacy and fame, you can’t have it both ways. There may be more fans like Mr Smedhs in her immediate future, and her security is something both she and the Palace will now have to consider.