It caused a revolution in the House of Windsor more than 20 years ago, and is now doing the same for the other European royal houses.
From Spain to Norway, Belgium to Denmark, royal families are fighting flagging public support by employing the "Diana effect" marrying princes off to glamorous young women to add sparkle, and usually controversy, to their otherwise dull families.
Many are commoners, some are from overseas, but the new wave of princesses is putting an end to speculation about the decline of European royalty. They are boosting popular support by adorning the front pages of magazines, and then coming up with the heirs: five European princesses have either just given birth, or are about to. As royal houses turn into soap operas not seen since the Charles and Diana show, royal mania is sweeping across Europe.
You may see the new commoner princesses in Hello!, Hola! or Paris Match, but not for their preening or partying. Instead, they are being hailed as modern, energetic ambassadors for their countries.
Crown Prince Felipe of Spain married a divorced television journalist, who presented her new-born baby, their first, to an adoring public on Monday. The Dutch Crown Prince Willem-Alexander married Maxima Zorreguieta, an Argentine commoner.
Crown Prince Frederik of Denmark married an Australian estate agent, who gave birth to a son last month. Crown Prince Haakon of Norway married a single mother, who has just announced that she is expecting their second child.
Not to be outdone, the Belgian court announced that Crown Prince Philippe and his wife, a former speech therapist, were expecting their third child, while his younger brother, Prince Laurent, and his British-born wife, Princess Claire, are expecting twins.
Richard Fitzwilliams, the former editor of International Who's Who, says that the injection of "non-royal" blood is refreshing royal households.
"The fact that they are marrying outside the royal and aristocratic strata can mean not only they are more aware of their subjects' lives, but they are more understanding of society as a whole," he said. "I do think that this is one reason why pretty well all these monarchies are going to last. These individuals are marrying for love."
Catholic Spain was outraged when Crown Prince Felipe, 37, announced that he intended to marry Letizia Ortiz, 32, a television journalist and a divorcee; but their glamorous "wedding of the century," followed promptly by the birth of baby Leonor, has sparked a new wave of monarchism in the country.
"Now she's produced an heir, that's a feather in her cap," Jane Walker, who reports on the Spanish Royal Family for Time magazine, said. "She is popular because she's made him happy. He's obviously over the moon. The minute they got engaged, he laughed and smiled a lot more than he used to. He just seemed to blossom."
In Denmark, Crown Prince Frederik's decision to marry Mary Donaldson, whom he met at a party in Sydney, Australia, was also greeted with opposition. Europe's oldest Royal Family, which has ruled for 1,100 years, would not survive such a shock, critics said; but Mary, who has learnt to speak Danish, has won the hearts of her future subjects.
"This is remarkable," Jens Henner, a constitutional lawyer, said. "A generation ago it would have been very difficult for a Danish crown prince to marry outside European royalty. That Mary is an Australian, a commoner and so incredibly popular shows how far we have moved."
Prince Frederik cut the umbilical cord and told reporters that he had cried when he saw his child. "You don't stand there and act like Superman," he said.
Their son is being looked after in the palace by Princess Mary and her parents. The first Australian to become a monarch has also sparked a new wave of monarchism in her old country. Unfortunately for Britain's Queen Elizabeth II, the Danish monarchy is now far more popular in Australia than her Royal Family.
For controversy, nothing matches Crown Prince Haakon of Norway's announcement that he was to marry Mette-Marit, who had no qualifications and already had an illegitimate child by a convicted drug addict. Even in Norway this was a bit much for their future Queen; but the glamorous blonde tearfully apologized for her wild ways during a television interview before the wedding and all was forgiven. She gave the Crown Prince his first child, Princess Ingrid Alexandra, last January, and is expecting their second.
Source: China Daily