LONDON (AP) — The coffin of Queen Elizabeth II left Buckingham Palace for the last time Wednesday, borne on a horse-drawn carriage and saluted by cannons and the tolling of Big Ben, in a solemn procession through the flag-draped, crowd-lined streets of London to Westminster Hall. There, Britain’s longest-serving monarch will lie in state for the world to mourn.

Her son, King Charles III, and his siblings and sons marched behind the coffin, which was topped by a wreath of white roses and her crown resting on a purple velvet pillow.

The queen will lie in state for four days until her funeral Monday, with hundreds of thousands of people expected to file past. Eight pall bearers carried the oak and lead-lined coffin into Westminster Hall, placing it on a raised platform known as a catafalque.

Shortly after 5 p.m., the first members of the public were allowed to file past the coffin. They moved in two lines, one on either side of the coffin.

One woman looked close to tears as she paused, faced the coffin and bowed her head.

The military procession from Buckingham Palace was designed to underscore the queen’s seven decades as head of state as the national mourning process shifted to the grand boulevards and historic landmarks of the U.K. capital.

Thousands who had waited for hours along The Mall outside the palace and other locations along the route held up phones and cameras, and some wiped away tears, as the procession passed. Applause broke out as the coffin passed through Horse Guards Parade. Thousands more sat in nearby Hyde Park watching on large screens.

The coffin was draped in the Royal Standard and topped with the Imperial State Crown — encrusted with almost 3,000 diamonds — and a bouquet of flowers and plants, including pine from the Balmoral Estate, where Elizabeth died on Sept. 8 at the age of 96.

Two officers and 32 troops from the 1st Battalion Grenadier Guards in red uniforms and bearskin hats walked on either side of the gun carriage. The 38-minute procession ended at Westminster Hall, where Archbishop of Canterbury Justin Welby led a service attended by Charles and other royals.

“Let not your heart be troubled: ye believe in God, believe also in me. In my Father’s house are many mansions: if it were not so, I would have told you,” Welby read from the Book of John.

After a short service, the captain of The Queen’s Company 1st Battalion Grenadier Guards, assisted by a senior sergeant, laid the royal standard of the regiment on the steps of the catafalque.

Four officers from the Household Cavalry – two from the Life Guards and two from the Blues Royals – began the first vigil around the coffin, taking their places at the corner and bowing their heads.

Thousands had queued up along the banks of the River Thames, waiting their turn to enter the hall and pay their respects.

The crowds are the latest manifestation of the nationwide outpouring of grief and respect for the only monarch most Britons have ever known after her 70 years on the throne.

Judth Nix, left her home in Leicestershire, central England, at 4:30 a.m. to stake out a place with a good view of the procession.

“We weren’t sure what to expect because we’ve seen clapping, we’ve seen ‘God save the King,’ we’ve seen ‘God save the Queen,’ so we didn’t know. But the silence was just unbelievable,” she said.

Maj. Gen. Christopher Ghika, of the Household division, who organized the ceremonial aspects of the queen’s funeral, said it was “our last opportunity to do our duty for the queen, and it’s our first opportunity to do it for the king, and that makes us all very proud.”

Troops involved in the procession had been preparing since the queen died. So had the horses of the King’s Troop Royal Horse Artillery.

Sgt. Tom Jenks, from the King’s Troop Royal Horse Artillery, said the horses were specially trained, including how to handle weeping mourners, as well as flowers and flags being tossed in front of the procession.

Heathrow Airport temporarily halted flights, saying it would “ensure silence over central London as the ceremonial procession moves from Buckingham Palace to Westminster Hall.”

President Joe Biden spoke Wednesday with Charles to offer his condolences, the White House said.

Biden recalled “the Queen’s kindness and hospitality” she hosted them and the first lady at Windsor Castle in June, the statement said. “He also conveyed the great admiration of the American people for the Queen, whose dignity and constancy deepened the enduring friendship and special relationship between the United States and the United Kingdom.”

Crowds have lined the route of the queen’s coffin whenever it has been moved in its long journey from Scotland to London.

On Tuesday night, thousands braved a typical London drizzle as the hearse, with interior lights illuminating the casket, drove slowly from an air base to Buckingham Palace.

Earlier, in Edinburgh, some 33,000 people filed in silent respect past her coffin as it lay for 24 hours at St. Giles’ Cathedral.

Hundreds of thousands are expected to visit the 900-year-old Westminster Hall, the oldest building in Parliament, for four days before her state funeral on Monday. By Wednesday afternoon, the line snaking along the banks of the River Thames was 2 1/2 miles long, according to a government tracker.

The hall is where Guy Fawkes and Charles I were tried, where kings and queens hosted magnificent medieval banquets, and where ceremonial addresses were presented to Queen Elizabeth II during her silver, golden and diamond jubilees.

Chris Bond, from Truro in southwest England, was among those waiting to see the queen’s coffin. He also attended the lying in state of the queen’s mother in 2002.

“Obviously, it’s quite difficult queuing all day long, but when you walk through those doors into Westminster Hall, that marvelous, historic building, there was a great sense of hush and one was told you take as much time as you like, and it’s just amazing,” he said.

“We know the queen was a good age and she served the country a long time, but we hoped this day would never come,” he added.

Chris Imafidon, secured the sixth place in the queue.

“I have 1,001 emotions when I see her,” he said. “I want to say, God, she was an angel, because she touched many good people and did so many good things.”

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Associated Press writer Sylvia Hui contributed.

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