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.

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 United Kingdom (UK) 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.

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 September 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.

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.

Joan Bucklehurst, a 50-year-old retail worker from Cheshire in northwestern England, said the queen “meant so much for everybody.”

“She was amazing, yeah,” she added, choking up with emotion. “So, we had to be here. We’ve been here a few times when there have been special occasions, but this one, I couldn’t miss this.”

Major General Christopher Ghika, of the Household division, who organised 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 have been preparing since the queen died. So have the horses of the King’s Troop Royal Horse Artillery.

Sergeant 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.

The hall is where Guy Fawkes and Charles I were tried, where kings and queens hosted magnificent mediaeval 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 lining up along the banks of the River Thames. 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 marvellous, 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 [of] a good age and she served the country [for] 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.”