By Gilbert Kreijger and Thomas Escritt
AMSTERDAM (Reuters) - Willem-Alexander became the first king of the Netherlands since 1890 on Tuesday, ascending a throne largely stripped of political power but still invested with enormous symbolic significance for the Dutch people.
At his investiture in Amsterdam's 600-year-old Nieuwe Kerk, or New Church, the 46-year-old monarch swore an oath to uphold the Dutch constitution and stressed the need for unity at a time of economic crisis.
"I take office in a period when many in the kingdom feel vulnerable or uncertain. Vulnerable in their job or in their health, uncertain about their income or their immediate environment," Willem-Alexander said at his inauguration, attended by crown princes and princesses and other dignitaries.
"We can no longer take it for granted that children will be better off than their parents ... Our strength is therefore not in isolation but by cooperating."
Willem-Alexander - who is a water management specialist, a useful expertise in a country where much of the land is below sea level - and his wife Maxima, a former investment banker from Argentina, are expected to bring a less formal touch to the monarchy at a time of national austerity and budget cuts.
April 30, or Queen's Day, has always been an occasion for partying in the Netherlands, and Amsterdam has been awash with orange - the color of the House of Orange - for days.
Houses were covered in bunting and flags and shop windows were stuffed with orange cakes, sweets, clothes and flowers.
Many people took Monday off work and started celebrating in earnest from Monday evening. Nearly a million people were expected at street parties in the capital where there was dancing to bands and DJs in a carnival atmosphere.
LIFTING THE MOOD
An estimated 25,000 people, many dressed in orange or wearing orange wigs, hats, feather boas and crowns, massed in Dam Square next to the Royal Palace to watch the abdication and inauguration being broadcast live.
Blinking back tears, former Queen Beatrix stepped out onto the balcony of the Royal Palace and presented her son to the crowds of cheering well-wishers.
"Some moments ago I abdicated from the throne. I am happy and thankful to present to you your new king," said Beatrix, 75, who retired after 33 years in the role, following in the tradition of her mother and grandmother. She now takes the title of princess.
The ceremonies provided a welcome excuse to celebrate at a time when plummeting house prices, rising unemployment and slumping consumer confidence have pushed the country into recession.
Prime Minister Mark Rutte said at the weekend the celebrations would lift the mood of the nation and might even have a positive economic impact.
The government had promised to keep the cost of the pageantry down - the ceremonies will cost about 12 million euros, excluding the bill for the extensive security measures.
"I've been pleasantly surprised by the new king, he seems to say exactly what you want him to say," said Alexander van Merchem, a student, craning his neck outside the church in the hope of seeing a passing dignitary.
"He seems like a really nice, pleasant guy."
Shop owner Marcel Beurst enthused about Queen Maxima.
"I'm really happy we're going to have a very nice new queen. Maxima has a great appearance, and she's a power woman. She'll manage things in the background. I think she'll be the real king."
Willem-Alexander wore a royal mantle decorated with silver lions that has been used for investitures since 1815, although it has been repaired and altered at least twice over the past century, for the investitures of his mother and grandmother.
In accordance with tradition, he was not formally crowned because in the absence of a state church, there is no cleric available to carry out the coronation. Instead, the crown and other jewels sat on a table beside him throughout the ceremony.
Queen Maxima wore a tiara and a full-length royal blue dress and cloak, which Dutch media reported was designed by Jan Taminiau of the Netherlands. The ceremony was attended by Britain's Prince Charles and his wife Camilla, and by Japan's Crown Prince Naruhito and Crown Princess Masako, on her first foreign trip since falling ill a decade ago.
Like their counterparts in Britain and Sweden, the Dutch royals are broadly popular; 78 percent of Dutch are in favor of the monarchy up from 74 percent a year ago, according to an Ipsos poll.
And like many other royals, they have had their fair share of embarrassing marital, political and financial scandals.
Willem-Alexander's marriage to Maxima in 2002 was controversial because Maxima's father, Jorge Zorreguieta, served in Argentina's military dictatorship more than 30 years ago.
Maxima quickly endeared herself to the Dutch, however - a poll showed she is now as popular as Beatrix, and even more popular than her husband.
While Beatrix had considerable political influence as queen, she was stripped of that power by an act of parliament last year, and the monarch no longer appoints the mediator who conducts exploratory talks when forming government coalitions.
(Writing by Sara Webb; Editing by Sonya Hepinstall)