So who should William woo?

The idea that Prince William and Kate Middleton are romantically involved seems based on superficial evidence. As flatmates and second-year students at St Andrews University, the pair are often seen together. Their attendance at a recent rugby tournament prompted an unnamed source to comment: "Their body language was very revealing. They looked very close." In contrast, the father of Miss Middleton commented: "People do not seem to realise that there are two girls and two boys sharing the flat at the university. They are together all the time because they’re the best of pals - and yes, cameramen are going to get photos of them together. But there is nothing more to it than that. We are very amused at the thought of being in-laws to Prince William, but I don’t think it is going to happen."

It’s clear the couple have much in common. Both are aged 20 and attended exclusive public schools; they share a love of sport and met while studying History of Art. But the Middleton family business, running a mail-order children’s party toys company, leaves them somewhat removed from the House of Windsor.

Kate Middleton is not the first girl to be linked to Prince William. Unlike his father, William has been allowed to choose his own girlfriends without the palace using the power of veto. At St Andrews he has also been linked to a fellow student, Bryony Daniels, the daughter of a wealthy landowner. The response from Daniels’s family to these rumours was dismissive, her mother saying: "They naturally see a fair amount of each other because they are studying the same things." Casual romances have been reported with businessman’s daughter Emilia d’Erlanger, who joined William on a cruise, and he has enjoyed the company of Arabella Musgrave, a stalwart of the polo circuit set. Tongues wagged when six girls were among the party of student friends the prince invited to Wood Farm, near Sandringham, for the weekend.

No-one could dispute that the heir to the throne would be quite a catch. He has inherited his mother’s good looks, and when he reaches 21 this summer he will be able to draw on a 2 million trust fund set up for him by the Queen Mother. At 25, he will get another 22 million trust. It is easy to visualise the kiss’n’tell dollies hanging out in the bars of St Andrews, hoping to snare themselves a prince.

But, a few natural lapses notwithstanding, William has been a picture of restraint during his time as a student, enjoying a few drinks in Ma Bells and the Gin House in St Andrews and being a regular at K Bar in Soho and Jak’s in Lower Sloane Street in London. In Cotswold pubs and restaurants he mixes with the polo set where there’s no shortage of pretty girls vying for his attention.

Parallels could be drawn with the summer of 1971, when a young Prince Charles was pictured chatting on the polo field with Camilla Shand. But for today’s young Royals, the rules of dating have changed. When Diana was first courted by Prince Charles, she was required to call him Sir, right up until their engagement. Prior to his relationship with Diana, Prince Charles played the field in full view of the press and the public eye.

An oft-quoted memorandum from Charles’s great uncle, Earl Mountbatten, written in 1974 said: "I believe in a case like yours that a man should sow his wild oats and have as many affairs as possible before settling down. But, for a wife, he should chose a suitable and sweet-hearted girl before she meets anyone else she might fall for." Mountbatten told Time magazine that Charles was always "popping in and out of bed with girls". Before his hunt for a suitable wife began, the Prince of Wales was romantically linked to a string of well-connected women, including Lady Jane Wellesley, Davina Sheffield, Sarah Spencer and Anna Wallace. Some were seen as "suitable"; others, such as Buddhist Zoe Sallis, were not. Charles’s courtship with Diana Spencer was played out in the media almost like an informal interview, guaging her suitability for a place in the monarchy. The nation watched every stage unfold as if it was a soap opera. Diana passed the initial test, but in the end turned out to be unsuitable, like so many other royal matches.

Edward VIII started the trend for falling in love with the wrong sort of girl when he married American divorcee Wallis Simpson. In recent decades Prince Andrew followed suit, first by falling for American Koo Stark, an actress who drew immediate comparisons to Simpson. Stark described it as "a relationship between two young people that was not dissimilar to any other love affair", but it soon turned to scandal after revelations that the actress had once starred in an erotic film.

Making Sarah Ferguson his wife was equally unsuccessful for Prince Andrew, as the lively redhead found it difficult to settle into the routine of royal life. Princess Diana soon emerged as another woman who found the demands of protocol and etiquette too much. Harold Brookes-Baker, publishing director of Burke’s Peerage, has said: "In any group you have to conform to the group rules and if you don’t then you don’t stay in that network for very long. In general, the aristocracy are not as open as other sections of society; they also tend to abide by a different set of rules, which if you are not from that section of society can be terribly divisive." For Diana and Sarah, the fairytale implications of marrying a prince turned out to be strictly fiction.

Today, the young Royals seem to be treading cautiously before committing themselves to marriage. Princess Anne’s children, at her insistence, do not have titles but they still rank high in social circles. Peter Phillips lived with American heiress Elizabeth Iorio for eight months and more recently had a four-month romance with air stewardess Tara Swain. His sister Zara and her live-in boyfriend, National Hunt jockey Richard Johnson, invited Hello! magazine to photograph their Cotswold home. Although the Phillips siblings are not subject to the same scrutiny as Prince William, the approach to their love lives seems unconstrained by protocol or parental pressure - the idea of "living in sin" would have been unthinkable a generation earlier.

As the world’s most eligible bachelor, Prince William will have to find a method of dealing with the inevitible media scrutiny. According to royal biographer Ingrid Seward in her book, William and Harry, William’s favourite chat-up line is: "Hi, I’m the future king, wanna pull?" He might give it an ironic inflection, but with public confessions of admiration from students and even pop princess Britney Spears, it’s an invitation plenty of eligible young ladies would jump at.

Having enjoyed a degree of privacy as a student at St Andrews, perhaps it’s not such a surprise that William has announced his intention to spend a few years living in the United States after he finishes his degree. Work in a gallery or auction house, and the possibility of a post-graduate degree, have apparently been discussed. Says a courtier: "William is determined to maintain a degree of anonymity and feels America offers him the best chance of that." This would be an unprecedented move. But William seems determined to forge his own path - he rarely undertakes royal duties and signs his cheques "William Wales".

The chance of a relationship surviving seems to decrease in proportion to the amount of time a person spends in the public eye. At the age of 20, William still has plenty of time to find the girl of his dreams, but it’s no surprise that he craves anonymity and independence. Having seen every detail of his parents’ relationship photographed, analysed and commented on, it seems clear that when he does embark on a serious relationship, Prince William will strive to keep it under wraps.