Queen Elizabeth II arrives at Westminster Hall to lie in state for 4 days before funeral

Sept. 14 (UPI) -- The casket carrying Queen Elizabeth II departed Buckingham Palace in London for the final time on Wednesday and began a procession that took the late monarch to the Houses of Parliament to lie in state for four days.

Thousands of Britons turned out to watch the queen's casket move along in the procession on a gun carriage, and hundreds of thousands are expected to visit the casket at some point at Westminster Hall over the next few days before her formal funeral on Monday.

The procession moved along the Thames River and wound through central London, along Queen's Gardens, the Mall, Horse Guards and Horse Guards Arch, Whitehall, Parliament Street, Parliament Square and New Palace Yard.

Members of the royal family walked behind the queen's casket, including King Charles III and the queen's other children -- Princess Anne, Prince Andrew and Prince Edward. Her grandsons Prince William and Prince Harry, Charles' sons, also trailed the gun carriage during the route.

Wednesday's procession and the queen lying in state are the first major ceremonial events in Britain since Elizabeth II died on Thursday at age 96 after 70 years on the British throne.

The casket left Buckingham Palace mid-Wednesday afternoon for the 40-minute procession. A gun salute at Hyde Park during the procession fired one round every minute.

Crowds of people began forming early Wednesday along the route as Britons wanted a chance to witness the historic event and honor the queen. Some staked out their positions overnight to ensure they had a good view. Thousands more gathered at Green Park with folding chairs and other items.

The Archbishop of Canterbury held a brief service after the queen arrived at Westminster Hall.

After the queen's arrival, the cross of Westminster was placed next to the coffin, which was adorned with the same imperial state crown that was worn by the queen after her coronation in 1952. The crown is made of gold and has nearly 3,000 diamonds and hundreds of pearls, sapphires, emeralds and rubies. It also contains the Black Prince's Ruby, the Stuart Sapphire and Cullinan II diamond.

A small group of anti-monarch protesters were arrested by London police on Wednesday. Labor Party leader Kier Starmer said demonstrators should show a "spirit of respect" for the late queen.

"Respect the fact that hundreds of thousands of people do want to come forward and have that moment," Starmer said according to The Guardian. "Don't ruin it for them. The word I'd use around that issue is respect.

"I think if people have spent a long time waiting to come forward to have that moment as the coffin goes past or whatever it may be, I think the respect that."

U.S. President Joe Biden had a phone call with King Charles III before the procession on Wednesday.

"The president recalled fondly the queen's kindness and hospitality, including when she hosted him and the first lady at Windsor Castle last June," the White House said in a statement. "He also conveyed the great admiration of the American people for the queen."