Mourners who wish to pay their respects to Queen Elizabeth II, who died last week at the age of 96, will be able to do so from Wednesday as she lies in state. Her casket will make its final journey today from Buckingham Palace to the Palace of Westminster, before her funeral at Westminster Abbey on Monday, Sept. 19.
The royal procession marks one of the last in a series of solemn ceremonies that have taken place since the Queen’s death. Her coffin, which will be transported by a horse-drawn gun carriage and flanked by King Charles III and other members of the Royal Family, will start at Buckingham Palace at 2:22 p.m. local time and will proceed half a mile down the flag-lined Mall, through the Horse Guards Parade, and down Whitehall until it reaches the Palace of Westminster. The procession will be followed by a short service led by the Archbishop of Canterbury, after which Westminster Hall will be opened for public viewing 24-hours a day for four days until 6:30 a.m. on the morning of her funeral.
Read More: What We Know So Far About Queen Elizabeth II’s Funeral
The last time Britain had someone lie in state—a formal tradition in which a closed coffin is placed in view so that members of the public can pay their respects—was for Queen Elizabeth II’s mother, who was also called Queen Elizabeth, in 2001. Then, as now, visitors must go through airport-style security and are only permitted to carry one small bag. It’s estimated that some 200,000 people paid their respects to the Queen Mother when she lay in state. For Queen Elizabeth II, British authorities are expecting closer to 1 million.
Mourners are already being warned that they could wait as long as 30 hours in a line stretching several miles long to pay their respects to the late Queen. Although volunteers, first-aid stations, and toilets will be dotted along the route, government guidance warns that mourners “will need to stand for many hours, possibly overnight, with very little opportunity to sit down, as the queue will keep moving.”
The influx of people is already being felt across London, where road and subway closures have been announced in the areas near where the procession will take place. Already faced with overcrowding problems, Transport for London, which operates the London underground service, has warned that it faces the biggest challenge in its history. The British government has advised commuters to avoid visiting the capital if they can.
Still, many Britons are undeterred, with some joining the line several days in advance in order to participate in what they consider to be a once-in-a-lifetime event.
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Write to Yasmeen Serhan/London at yasmeen.serhan@time.com