In a sombre, regal procession, Queen Elizabeth II's flag-draped coffin was driven slowly through the Scottish countryside from Balmoral Castle to the Scottish capital of Edinburgh.

Mourners packed city streets and highway bridges or lined rural roads with cars and tractors to take part in a historic goodbye to the monarch who had reigned for 70 years.

The hearse drove past piles of bouquets and other tributes as it led a seven-car cortege from Balmoral, where the Queen died on Thursday at age 96, for a six-hour trip through Scottish towns to the Palace of Holyroodhouse in Edinburgh.

The late Queen's coffin was draped in the Royal Standard for Scotland and topped with a wreath made of flowers from the estate, including sweet pea, one of her favourites.

The procession was a huge event for Scotland as the UK takes days to mourn its longest-reigning monarch, the only one most Britons have ever known. People turned out hours early to grab a space by the police barricades in Edinburgh. By afternoon, the crowds were 10 people deep in places.

Princess Anne curtsies the coffin of Queen Elizabeth II, draped with the Royal Standard of Scotland, as it arrives at Holyroodhouse, Edinburgh. Photo / Jacob King via AP

"I think she has been an ever-constant in my life. She was the Queen I was born under, and she has always been there," said Angus Ruthven, a 54-year-old civil servant from Edinburgh. "I think it is going to take a lot of adjusting that she is not here. It is quite a sudden thing."

Silence fell on the packed Royal Mile in Edinburgh as the hearse carrying the coffin arrived. But as the convoy vanished from view, the crowd spontaneously started clapping.

When the hearse reached Holyroodhouse, members of the Royal Regiment of Scotland, wearing green tartan kilts, carried the coffin past the Queen's youngest three children —Princess Anne, Prince Andrew and Prince Edward — and into the throne room, where it was to remain until Monday afternoon so staff can pay their last respects.

• Queen of our currency: What happens to our bank notes and coins?
• Queen Elizabeth's death: Promise kept until the very end
• Queen's death: Govt considering public holiday

King Charles III and his Queen Consort Camilla will travel on Monday to Edinburgh to join another solemn procession that takes the Queen's coffin to St Giles Cathedral on the city's Royal Mile. There the coffin will remain for 24 hours so the Scottish public can pay their respects before it is flown to London on Tuesday.

Pallbearers carry the coffin of Queen Elizabeth II, draped with the Royal Standard of Scotland, as it arrives at Holyroodhouse. Photo / Alkis Konstantinidis via AP

Meanwhile, it was announced President Joe Biden has formally accepted an invitation to attend the state funeral service for the Queen. The White House said on Sunday that the President will be accompanied by First Lady Jill Biden. The service will be held on September 19.

The first village the cortege passed through was Ballater, where residents regard the royal family as neighbours. Hundreds of people watched in silence and some threw flowers in front of the hearse.

"She meant such a lot to people in this area. People were crying, it was amazing to see," said Victoria Pacheco, a guest house manager.

In each Scottish town and village, the entourage was met with muted scenes of respect. People stood mostly in silence; some clapped politely, others pointed their phone cameras at the passing cars. In Aberdeenshire, farmers lined the route with an honour guard of tractors.

Along the route, the cortege passed through locations laden with House of Windsor history. Those included Dyce, where in 1975 the Queen formally opened the UK's first North Sea oil pipeline, and Fife, near St Andrews University, where her grandson Prince William, now the Prince of Wales, studied and met his future wife, Catherine.

Crowds line the Royal Mile in Edinburgh waiting for the hearse carrying the coffin of Queen Elizabeth II. Photo / Jane Barlow via AP

Sunday's solemn drive came as the Queen's eldest son was formally proclaimed the new monarch — King Charles III — in the rest of the nations of the United Kingdom: Scotland, Wales and Northern Ireland. It came a day after a pomp-filled accession ceremony in England.

"I am deeply aware of this great inheritance and of the duties and heavy responsibilities of sovereignty, which have now passed to me," the King said on Saturday.

Just before the proclamation was read on Sunday in Edinburgh, a protester appeared with a sign condemning imperialism and urging leaders to "abolish the monarchy". She was taken away by police. Reaction was mixed. One man shouted, "Let her go! It's free speech!" while others shouted: "Have some respect!"

Still, there was some booing in Edinburgh when Joseph Morrow, Lord Lyon King of Arms, finished his proclamation with the words "God save the King!"

Ann Hamilton, 48, said she thought the booing was "absolutely terrible".

Sophie, the Countess of Wessex and Prince Edward and others await the hearse carrying the coffin of Queen Elizabeth II. Photo / Alkis Konstantinidis via AP

"There's tens of thousands of people here today to show their respect. For them to be here, heckling through things, I think it was terrible. If they were so against it, they shouldn't have come."

Still, it was a sign of how some, including Britain's former colonies, are struggling with the legacy of the monarchy.

Earlier, proclamations were read in other parts of the Commonwealth, including New Zealand and Australia.

Charles, even as he mourned his late mother, was getting to work at Buckingham Palace, meeting with the secretary-general and other representatives of the Commonwealth. Many in those nations are grappling with affection for the Queen and lingering bitterness over their colonial legacies, which ranged from outright slavery to corporal punishment in African schools to looted artifacts held in British cultural institutions.

Australian Prime Minister Anthony Albanese, who had started laying the groundwork for an Australian republic after an election in May, said Sunday that now was the time not for a change but for paying tribute to the late Queen.

King Charles III is seen leaving Buckingham Palace. Photo / Zac Goodwin via AP

India, a former British colony, observed a day of state mourning, with flags lowered to half-staff on all government buildings.

Amid the grief enveloping the House of Windsor, there were hints of a possible family reconciliation. Prince William and his brother Harry, together with their respective wives, Catherine, Princess of Wales, and Meghan, Duchess of Sussex, delighted mourners near Windsor Castle with a surprise joint appearance Saturday.

The Queen's coffin was taking a circuitous journey back to the capital. After it is flown to London on Tuesday, the coffin will be moved from Buckingham Palace on Wednesday to the Houses of Parliament to lie in state until a state funeral at Westminster Abbey on Sept. 19.

In Ballater, the Rev David Barr said locals consider the royals as neighbours.

"When she comes up here, and she goes through those gates, I believe the royal part of her stays mostly outside," he said. "And as she goes in, she was able to be a wife, a loving wife, a loving mum, a loving gran and then later on a loving great-gran — and aunty — and be normal."

People stand in line after laying flowers for Queen Elizabeth II in front of Buckingham Palace. Photo / Nariman El-Mofty, AP

Elizabeth Taylor, from Aberdeen, had tears in her eyes after the hearse carrying the Queen's coffin passed through Ballater.

"It was very emotional. It was respectful and showed what they think of the Queen," she said. "She certainly gave service to this country, even up until a few days before her death."