A brand new chapter for the heirs of Grace

Once upon a time, a Prince married a movie star and they had three beautiful children - who went off the rails. After years of royal fecklessness and bad behaviour, Sholto Byrnes asks if the next generation of Grimaldis can restore order to the court

As Princess Caroline's daughter Charlotte Casiraghi wakes up to her 18th birthday today, she knows that all Monaco will be devouring details of her three-day coming-of-age celebrations last weekend. The annual Red Cross Ball on Friday, where she will make her debut in the Euro society atop which the Monegasque princely family perches like a gaudy decoration, will be another occasion for Grimaldi watchers to inspect her and her elder brother Andrea.

For just as attention is increasingly shifting from our Queen's middle-aged children, the public having wearied of their divorces, freeloading and petty pomposities, and moving on to the new generation of Princes William and Harry and their unstuffy-sounding cousins Peter and Zara Phillips, so Princess Caroline's children are seen as the likely future of the House of Grimaldi. Charlotte could be the "new Grace", they say.

Under the terms of a 1918 treaty, if the ruling prince died without producing an heir, Monaco would become part of France. However, as the heir, Prince Albert, has shown so little enthusiasm for marriage, let alone siring children, that rumours have sprung up that he is gay (he denies it), the current ruler, Prince Rainier, changed the constitution so that his daughters Caroline and Stephanie and their children could join the line of succession.

Despite Caroline's wish to keep her children out of the public eye, the effortless style and good looks of Charlotte and 20-year-old Andrea (their younger brother, Pierre, is 16), and the prospect that one of them may one day reign in Monaco, have drawn the cameras and the gossips. Andrea, now third in line to the throne, has not so far proved himself to be the hardest-working member of the family. His assiduous devotion to watersports is evidently not matched by an equal hunger for knowledge - he failed his baccalaureate last year (shades of Prince Harry?). He has, however, shown a romantic streak, buying one girlfriend a miniature pot-bellied pig as a present, and giving another, the American singer Kaci, a diamond ring worth £250,000.

This is not the world of the dowdy, penny-pinching Windsors. Charlotte, for instance, was given an island off Sardinia for her fifth birthday. When she was eight, the designer Karl Lagerfeld, a family friend, remarked that she reminded him of Brigitte Bardot. A keen horsewoman, raised, like her brothers, in the quiet town of Saint-Rémy-de-Provence, where the family moved after the death of Caroline's second husband, Stefano Casiraghi, she has become a teen fashion icon in France, admired for her restraint and elegance.

Although the achievements of the next generation of Monaco royals may have been limited so far to the sporting arenas and the playgrounds of the European rich, they make a very favourable contrast with the balding Albert and the ever wayward Stephanie, who continues to make the headlines for all the wrong reasons. The latest tale to emerge is that she has split from her second husband, the trapeze artist Adans Peres. This may spell the end of an act in which Stephanie's daughter Pauline is hoisted into the air by an elephant. But the princess will still have a connection to the circus as its owner, Franco Knie, is an ex-boyfriend whom she squeezed in between a marriage to her bodyguard and a fling with her father's butler.

This may sound most unlike our own rather staid royal family, but it is not so terribly out of the ordinary for the Grimaldis, the princely dynasty that has ruled a square mile on the Mediterranean since 1297. As His Serene Highness Prince Rainier once put it: "Royal scandal is as old as the notion of royalty itself. Check the history books." Rainier might have to concede, though, that with a cast including playboys, nightclub owners, a prince given to public micturation and a cameo by Miss Bare Breasts Belgium, his family has contributed more chapters than most in recent years.

In contrast to its future wealth, which is derived partly from its favourable tax laws, the country bequeathed to Rainier in 1949 was in a poor financial state, its tourism and gambling industry threatened by new rivals on the French Riviera and its reputation tarnished by a wartime alignment with the collaborationist Vichy regime. The situation began to improve when Aristotle Onassis sailed into the harbour in 1951, but the involvement of the Greek tycoon in the principality's affairs brought trouble in its wake, too; Onassis proceeded to take over the Société des Bains de Mer, which owned the casino, the beach resort and many other tourist attractions, giving him rather more control over what happened in Monaco than Rainier liked.

The curtain of obscurity that had hitherto hidden the Ruritanian doings of the Grimaldis was removed instantly at the beginning of 1956 with the announcement of Rainier's engagement to Grace Kelly. "A prince and a movie star. It's pure fantasy," said Onassis, who, along with Monaco's National Council, was keen that Rainier should marry a famous woman to bring more attention to the principality.

The actress made the transition to Princess Grace, first lady of Monaco, very successfully. Despite finding the protocol overly stuffy at times, and resenting the fact that she could not make any more films because it was not thought seemly given her new status - as well as being unhappy at times during her marriage to Rainier, amid unproven rumours of mutual infidelity - nevertheless, Grace wore the mantle of royalty easily.

This was fortunate, as the Grimaldis are very royal (even though technically they are not, being merely princely, which is why they are "serene" rather than "royal" highnesses). Of the children, the most regal is Caroline. Even as a child there was a haughtiness to her. A palace functionary responsible for taking her to lessons remembers that Caroline would call her, declare disdainfully that she was awake, and then put the phone down without waiting for a reply. Asked by Grace why she didn't sign up to a cookery course at Maxim's restaurant in Paris, a 17-year-old Caroline was scornful. "I don't need to, Mummy," she said, "we've got slaves to do that."

Caroline may have attained a calmness with her third husband, Prince Ernst of Hanover, but her past is almost as colourful as that of her sister. At 21, Caroline took up with Philippe Junot, a feckless playboy 17 years her senior. Rainier and Grace were aghast when it became clear that she intended to marry him. Grace's friend and biographer Gwen Robyns said of Junot: "His remarks are too trite. His teeth are too bright. And his crotch is too tight."

Rainier's worries were justified almost immediately. When the couple set off on honeymoon, Caroline was dismayed to find that a photographer had been hired to go to Tahiti with them. Junot later sold the pictures without telling her. Grace predicted the marriage would be over in two years; it was.

Next up was Stefano Casiraghi, three years younger than Caroline and the heir to an Italian oil business. His definition of "work" seemed a little vague, too, but Rainier was pleased by his devotion to Caroline and made him a Duke of Monaco after the marriage. The couple had three children - Andrea, Charlotte and Pierre - but in 1990 Casiraghi died in a speedboat accident.

Her third husband, Prince Ernst of Hanover, was a man whom Grace had originally hoped her daughter would marry. If the late princess were still alive, however, she might have changed her mind about him. Under Salic law (which prohibits succession in the female line), Ernst would be the British king rather than just the Prince of Hanover. That Salic law does not apply in Britain is fortunate, as the prince's exploits include relieving himself on the Turkish tent at the Hanover Expo 2000, being fined £7,000 for kicking a sound engineer, assaulting journalists, beating up a disco manager, and throwing mozzarella round a Salzburg restaurant, hitting a baron on the head in the process.

Neither Ernst's behaviour nor the fact that he had a wife (who was one of Caroline's friends) proved an obstacle, and in 1999 the pair were married, the union raising Caroline from the style of "Her Serene Highness" to "Her Royal Highness".

From the moment of her birth, Stephanie seemed destined to be the liveliest and most vexatious of the younger Grimaldis. After suffering several miscarriages, Grace declared that the family's new addition "shall have everything she wants". While she had imposed discipline on the two elder children, she was much easier with Stephanie, leading Grace to admit that by her teens her youngest had become "a royal pain in the ass". She added: "I should have been beating her like a gong long ago."

After Stephanie left school, she enrolled in the Institute of Fashion Design in Paris, but then announced that she and her boyfriend Paul Belmondo, son of the actor Jean-Paul Belmondo, wanted to learn to become racing drivers instead. It was at the end of that weekend that Grace, who rarely drove herself, insisted on taking the wheel for the journey from the family's Alpine retreat, Roc Agel, back to the Palace. Stephanie was in the car with her, and for years after the crash in which her mother died faced whispers that it was she who had been driving, although there was no evidence to suggest that this was the case.

In the following few years, during which Stephanie became even less inclined to toe the royal line, she enjoyed brief careers in modelling, swimwear design, pop music (one single sold a million copies in France), and equally brief flings with a series of men of distinctly unprincely material. Among these were the actor Rob Lowe and Mario Oliver, a nightclub owner who had received a suspended sentence for sexual battery. Caroline in particular disapproved of Oliver, who was not allowed to enter the palace in Monaco, and was delighted when this romance ended. For Stephanie, however, the parting proved painful, not least because she had to have surgery to remove a tattoo of his initials from her buttocks.

By 1992 Stephanie had begun an affair with her bodyguard, Daniel Ducruet, with whom she had two children out of wedlock. When her son, Louis, was born, none of the Grimaldis visited her in hospital, and Stephanie was not present at Rainier's 70th birthday celebrations the following year. In 1995 Ducruet asked Rainier for permission to marry Stephanie, and for a while the rift in the family seemed to have been healed. The happy scenario came to an end, however, after Ducruet was filmed making love to one Fili Houteman, a lady who rejoiced in the title of Miss Bare Breasts Belgium 1995. When pictures of Ducruet and his friend's prize-winning assets were sold to the worldwide press, divorce was inevitable.

In 1998 Stephanie had another child, Camille. The father has never been acknowledged, but is widely thought to be another palace bodyguard, Jean-Raymond Gottlieb. Not long after she took up with Franco Knie, a circus owner and elephant trainer. So strongly did Knie, who was married with three children, empathise with his charges that he was known to pass time in his trailer wearing a pair of briefs with an elephant's trunk attached to it. But even this was not enough to keep Stephanie travelling with his circus, and soon she moved on first to a palace butler, and then a palace gardener. By this point, it is said, several of the wives of male palace staff were beginning to feel nervous about the princess's presence. Their worries ended last year when Stephanie married again, this time to Adans Peres, a performer in her former beau's circus. Despite her split from Peres, the palace wives may still be safe, as it is thought that she is again seeing Ducruet.

If the love lives of Caroline and Stephanie have caused Prince Rainier much heartache, it is the lack of anything serious in that department that has been the worry over Prince Albert. Groomed from an early age in the responsibilities of the heir to the Monegasque throne (his upbringing was supervised mainly by Rainier while the girls were left to Grace), Albert is by all accounts pleasant, reasonably bright by royal standards, and a keen sportsman. He has brought many international sporting and musical events to Monaco, and headed the principality's delegation when it was accepted into the United Nations in 1993. Although he has been "linked" to many famous women such as Brooke Shields and Claudia Schiffer (such links often consisting of little more than a couple of dinner dates), he has yet to settle down. And since he is now 46, he is seen to have failed so far in performing his most important royal duty - producing an heir of his own.

It is for this reason that Rainier changed the constitution to include his other children and grandchildren in the line of succession. Unless Albert marries and does his princely duty, the focus will fall all the more on his nephew Andrea, and niece Charlotte. Andrea has something of the Prince William about him, and must surely be reluctant to step into such a harsh limelight. But with a stepfather like Prince Ernst to guide him, he can hardly fail to produce more episodes in the very public soap opera that is the Monaco royal family. Deo juvante, as the Grimaldi motto goes - with god's help.