LONDON — One by one, they stood before the coffin, straightening their backs, squaring their shoulders, pulling in their shirttails. Most bowed their heads, some curtsied and others blew kisses. Many blessed themselves. A few, wearing military caps, raised their hands in a crisp salute.
Tens of thousands of people waited up to 24 hours to pay their final respects to Queen Elizabeth II on Saturday, their individual acts of mourning commingling into a vast national expression of bereavement.
It was the third day the queen’s body lay in state under the ancient vaulted timber roof of Westminster Hall. With foreign leaders and royalty arriving in London for her funeral on Monday, the endless river of ordinary people was joined by dignitaries from the sovereign’s far-flung realms: Prime Minister Justin Trudeau of Canada and Prime Minister Anthony Albanese of Australia.
At 6 p.m., Prince William and Prince Harry took up positions next to the catafalque to stand vigil over their grandmother, who died on Sept. 8. Both wore military uniforms — Harry having received special permission from his father, King Charles III, to do so, despite relinquishing his honorary military titles when he withdrew from royal duties and moved to Southern California with his U.S.-born wife, Meghan.
Harry, who served as a helicopter pilot in Afghanistan and prizes his ties to the military, has worn a morning suit in other official ceremonies during the 10-day mourning period for the queen. A spokesman for the prince, who is also known as the Duke of Sussex, had said Harry was content to wear civilian clothes.
The brothers were joined at the catafalque by their six cousins, the children of Princess Anne, Prince Andrew and Prince Edward.
Earlier on Saturday, William, the Prince of Wales, joined the king in an impromptu visit to people who had spent the night in the line — or as the British have branded it over the past two days, “The Queue.” As the two shook hands, the somewhat bedraggled crowd broke into cries of “God save the king” and “hip, hip, hooray!”
Told that a woman had been waiting for 12 hours, William said, “You look very well.” After one handshake, he said, “Very warm hands,” drawing laughs when he complimented the person for dressing properly for the overnight chill.
For some, though, the wait was too much. By Saturday afternoon, paramedics had treated several hundred people, most for complaints about dehydration or feeling faint. Dozens of people were taken to hospitals. With temperatures forecast to fall to 47 degrees overnight on Sunday, the police warned people to bundle up.
The Queue, which snakes across the Thames and winds for miles along the river’s south bank to Southwark Park, has quickly become a kind of cultural phenomenon. Many view it as the ultimate expression of British democracy. The soccer star David Beckham got credit on social media for lining up like everyone else.
While most people in line appeared to be good humored and well behaved, one man was accused of exposing himself and pushing into people in the crowd, according to the BBC. He was charged with two counts of sexual assault.
The queen’s coffin will lie in state at the Palace of Westminster until Monday morning, when it will be carried to Westminster Abbey for the funeral service. On Saturday, the authorities in London were girding themselves for the one of the greatest public events ever in a city that has thrown royal weddings, Olympic Games and, just in June, a four-day Platinum Jubilee to mark the queen’s 70 years on the throne.
Among the logistical challenges will be coordinating the visits of hundreds of foreign heads of state and other dignitaries. Mr. Trudeau’s motorcade navigated past heavy crowds on Saturday as he left Westminster Hall after paying his respects to the queen. Later, he headed to Buckingham Palace, where King Charles played host at a reception for prime ministers of countries in the realm.
President Biden and the first lady, Jill Biden, were expected to arrive in London on Saturday night. There are no plans for him to meet with Prime Minister Liz Truss during the visit, Downing Street said on Saturday. Instead, Ms. Truss will meet with Mr. Biden for the first time as prime minister on Wednesday in New York City, where both will be attending the meeting of the United Nations General Assembly, her office said.
The mood among the crowds in London was calm, though the police were on high alert. When a young man on a bike careered down a closed road a block from Westminster Hall, an officer tackled him to the ground, to cheers from the crowd. He was led away by the police, apparently unharmed.
Many of those who had lined up milled in the square outside Parliament afterward, chatting and taking selfies with the recently renovated Big Ben. It was a heterodox crowd, some clad in T-shirts and jeans, while others wore morning suits. Among the V.I.P.s who paid their respects was Michael Heseltine, who served as deputy prime minister and played a role in the downfall of Prime Minister Margaret Thatcher.
Inside Westminster Hall, however, the hush was palpable, broken only by the footfall of guards on the stone floor, as they rotated the duty of standing vigil by the coffin every 20 minutes. Shuffling out of the hall, many in the crowd wiped tears from their eyes. Others comforted each other with a pat on the back or an arm thrown over a shoulder.
And for almost all: a mournful backward glance at the coffin of a beloved queen before they emerged back into the sunlight.
Isabella Kwai contributed reporting.