Prime Minister Frederiksen expressed “a deepfelt and devoted thanks” to Queen Margrethe on behalf of the nation.

“To be queen and king is a link in a more than thousand-year-long chain. When one steps aside, the next is standing at the ready. And the crown prince that now becomes our monarch is a king that we know, a king that we like, and a king that we trust,” she said.

Among the thousands lining the capital was 45-year-old Kasper Wiigh Larsen. “It brought tears in a joyful way to see him do so well up on the balcony, both with his speech and when Mary came out and held his hands and finishing with a kiss,” he told Reuters.

Britain’s King Charles III – who had his coronation last summer – has congratulated the new king and queen.

“I look forward to working with you on ensuring that the enduring bond between our countries, and our families, remains strong, and to working together with you on issues which matter so much for our countries and the wider world,” he said in his message.

Margrethe, 83, was Europe’s longest-reigning monarch and the world’s last reigning queen. She announced her historic tenure would come to an end after 52 years in a stunning live address on New Year’s Eve.

She said she had been reflecting on “whether now would be an appropriate time to pass on the responsibility to the next generation” following a recent surgery on her back and had come to the decision “that now is the right time.”

The queen appeared emotional herself and said “God save the King” after she put down her signature to the Council of State, handed over the throne, and then exited the room.

Although no longer the ruling monarch, Margrethe will continue to be titled as Her Majesty and can be installed as acting regent, according to the Danish Royal House. This means that she will be able to perform duties as head of state when both King Frederik or Crown Prince Christian are not able, such as if they were overseas. Other Danish royals who can also assume the role of acting regent if required include Mary, Frederik’s brother Prince Joachim and his aunt, Princess Benedikte.

While the Danish monarchy is one of the oldest in Europe, stretching back more than 1,000 years, there is no traditional crowning moment. As such, world leaders and high-profile dignitaries were not in attendance, with the Danish changeover being a significantly more low-key occasion in comparison to the global spectacle and pageantry of King Charles III’s coronation in May.

Still, the streets were crammed with well-wishers enjoying the spectacle.

Denmark is a constitutional monarchy, and its royals perform an important but symbolic ambassadorial role in addition to signing off any new legislation. Formal powers lie with the elected parliament and its government based at Christiansborg Palace in the heart of the capital, Copenhagen.

And it was here that King Frederik X visited for the last time as crown prince on Sunday, and departed as the ruling monarch of Denmark, Greenland and the Faroe Islands.

Birgitte Borup, culture editor at Danish newspaper Berlingske, told CNN the transition between monarchs will feel “very different” to 1972 “simply because the queen is alive.”

“It’s the first time in 900 years a Danish king or queen has abdicated. It will be a more festive occasion than the last time when a young Margrethe took over,” she explained. “The queen’s decision to abdicate was shocking but most Danes seem to understand that she wants to pass on the torch due to declining health.”

It’s incredibly rare for a monarch to abdicate in Denmark. The last Danish monarch to do so was King Eric III when in 1146 he relinquished the crown to join a monastery. But the practice is more common in other European royal houses.

Borup said Denmark was “entering a new modern era” and while Frederik has enjoyed broad support from Danes during his time as crown prince, as monarch he will have work to do.

“He might continue making the monarchy more accessible to the people. His main challenge will be maintaining a popular and relevant monarchy in the years to come.”