To the sound of military bands and under a sunny sky, the 77-year-old monarch, clad in a sober suit and tie, enjoyed the public acclaim along with Queen Silvia, 79, wearing a canary yellow ensemble, as six horses led the royal procession.

The crowd broke into applause as they passed and waved Swedish flags to mark the milestone for Carl Gustaf, who was the world’s youngest monarch when he was crowned aged 27 in September 1973 after the death of his grandfather Gustaf VI Adolf.

The king is the longest reigning monarch in Sweden’s history and also the European monarch with the second-longest reign, behind his cousin Queen Margrethe of Denmark who took the throne in 1972.

Born on April 30, 1946, Carl Gustaf Folke Hubertus Bernadotte was only nine months old when his father, Prince Gustaf Adolf, died in a plane crash in Denmark.

Central Stockholm was closed to traffic with police expecting crowds across the day to top several hundred thousand — though celebrations went ahead amid tight security given that Sweden last month raised its terror alert level following a spate of Koran burnings that have angered the Muslim world.

Christina Flodin, an administrator aged 59, was among admirers of the king, who Friday oversaw the changing of the guard at the palace ahead of a gala banquet for business and religious leaders and other Scandinavian royals. 

 ‘Continuity, stability’

“I am there to celebrate his 50 years with him — I want to show my gratitude for all he has done,” she told AFP, saying he represents in her view “continuity, stability, a good model leader.”

“I came for my brother who is in the navy and participating in the parade,” said Wendela Seppi, a machine operator aged 23. “It’s a bit unreal — I find it’s cool something’s happening” in Stockholm.

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The afternoon procession through the capital was the highlight of the celebrations, their horse-drawn carriage escorted by 3,000 troops from the army, navy and air force and military bands.

The final leg of the procession was to see them being rowed across the water in the royal barge to the steps below the palace in the Old Town, with an outdoor concert nearby featuring several popular Swedish acts to top off the day, from Cuban salsa to disco and classic Swedish sounds.

The city centre was transformed into a giant public dance floor to allow residents to let their hair down.

Despite occasional scandals — the biggest when a 2010 book alleged he frequented sex clubs and had numerous affairs — the king enjoys broad support in his homeland.

A poll this month in Swedish newspaper Dagens Nyheter said 62 percent of Swedes were in favour of the monarchy, a level that has remained stable over two decades.

READ ALSO: LISTEN: King’s 50th jubilee, and must Swedish citizenship be ‘protected’?

The king’s role has been purely ceremonial since constitutional reform in 1974.

“We must not abolish the monarchy,” said Martin Persson, a 60-year-old bus driver. “I think it’s good — and I’m hoping to see him today,” said Persson, from the western coastal town of Vastra Gotaland. 

The palace has remained tight-lipped about the cost of the festivities.

As far as presents for his majesty are concerned, Swedish furniture retailer Ikea is gifting the man who already has a throne a special armchair to mark the occasion.

The retro design comes from the “1970s when the king met Silvia at the Olympic Games in Munich,” Ikea executive Johan Ejdemo told AFP.