Margrethe left the room with tears in her eyes, saying: “God bless the king.”

Denmark, one of the oldest monarchies in the world, does not have a coronation but there were still moments of pomp in the day’s events.

After the abdication, the new monarch was proclaimed king by Prime Minister Mette Frederiksen on the balcony of the parliament building, Christiansborg castle, with the words: “Long live his majesty King Frederik the 10th.”

Wearing a ceremonial military uniform adorned with medals, Frederik addressed the crowd from the balcony.

“My hope is to become a unifying king of tomorrow. It is a task I have approached all my life. It is a task I take on with pride, respect and joy,” he said.

Visibly moved and several times wiping tears from his eyes, Frederik ended his speech with the words: “United, committed, for the Kingdom of Denmark,” his royal motto, a 500-year old tradition supposed to underpin a new monarch’s reign.

Frederik was joined on the balcony by his Australian-born wife Mary, 51, who is now queen, and their children: Christian, 18, who is the new heir to the throne, Princess Isabelle, 16, and 13-year-old twins Princess Josephine and Prince Vincent.

The royal couple, who met in Sydney during the 2000 Olympic Games, kissed before leaving the balcony amid roaring cheers from the tens of thousands of people who had converged on the capital in close to freezing temperatures.

“They did so well. I think it was so nice that they ended with a kiss, the whole square was oozing with love and joy in that moment,” said one woman who gave her name only as Marie.

The new king and queen take the throne at a time of huge public support and enthusiasm for the monarchy in the nation of nearly six million.

“It’s just exciting that an ordinary person like us becomes a queen. It’s very exciting!” said Judy Langtree, a retiree waiting outside Christiansborg who flew with her granddaughter from Brisbane, Australia to watch the succession.

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Despite the freezing winter weather, huge crowds had gathered along the procession route and outside Christiansborg, bundled up in warm parkas and some wrapped in Danish flags to catch a glimpse of the new sovereign.

Copenhagen police closed several metro stations in central Copenhagen for security reasons to stop more people from entering the packed streets.

The new king and queen will continue to live with Margrethe, who will retain her title as queen, in Amalienborg albeit in their respective palaces in the octagonal complex.

Margrethe, who had said in the past she would remain on the throne for life, did not give a reason for her decision to step down but said that a major back surgery she underwent in February had made her consider her future.

This is only the second time a Danish sovereign has stepped down – the last one was Erik III, almost nine centuries ago in 1146.

Aske Julius, a 27-year-old Copenhagen resident, called Margrethe “the embodiment of Denmark … the soul of the nation”.

“More than half of the Danish population has never known anything else but the queen,” he said.

Portraits and banners around the capital thanked the queen for her years of service, with cheeky signs in the metro declaring “Thanks for the Ride, Margrethe”. Others read “Long Live the King”.

Apart from the abdication, the protocol was largely similar to previous royal successions in Denmark. No foreign dignitaries or royals were invited, and there is no coronation or throne for the new monarch.

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Margrethe chose to abdicate exactly 52 years to the day after she took over from her father, Frederik IX.

“There’s a lot of symbolism around this day,” Cecilie Nielsen, royal correspondent for Danish public broadcaster DR, said.

The queen stunned Danes when she announced her abdication in her annual televised New Year’s Eve address, after having repeatedly insisted she would follow tradition and reign until her death. Even her own family was only informed three days prior.

Experts say that passing the baton to her son now will give him time to flourish in his role as monarch, after gradually taking on increasing responsibilities.

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“She thinks the crown prince is totally ready to take over. And she wants to avoid a situation like in Great Britain where Prince Charles became King Charles after the age of 70,” historian Lars Hovbakke Sorensen said.

Like his mother, Frederik, who had been crown prince since the age of three, enjoys the support of more than 80 per cent of Danes.

He is expected to bring his own style to the monarchy, which dates back to the 10th century Viking era.

“He understood that he could not copy (the queen) and has managed to define his own image, his own ties to the Danish people,” another historian, Bo Lidegaard, said.

While his mother is known for her love of the arts and is an accomplished writer and artist, Frederik is an avid sportsman who champions environmental causes.

In Denmark the monarch’s role is largely ceremonial, but he or she does sign legislation, formally presides over the forming of a government and meets the cabinet regularly.

Additional reporting by Reuters