One of the biggest logistical events ever witnessed in London is underway on Thursday as the first few thousand members of the public file past the coffin of Queen Elizabeth II, Lying-in-State at Westminster Hall in the Houses of Parliament complex in the heart of the UK capital.
A week since the 96-year-old monarch died peacefully at her Scottish summer residence of Balmoral Castle, her coffin has been part of a historic journey by road and air until it was conveyed in a grand procession from Buckingham Palace to lie in state in the historic hall within the Palace of Westminster.
The ancient ceremony of Lying-in-State, dating back to the 19th century, involves the coffin resting on a raised platform called catafalque in the middle of Westminster Hall as members of the queuing public are allowed in to walk briskly past. Lying-in State is a tradition in which the body of the deceased is placed in a state building either in a coffin or outside, for members of the public to be able to pay their respects. If the coffin is lying in a location other than the principal government building, it may be called lying in repose.
Within hours of the Lying-in-State ceremony opening to the public at 5pm local time on Wednesday evening, the queue was said to be over 4-km-long winding around the river Thames.
According to the Department of Digital, Media and Sports (DCMS), which is coordinating the logistical aspect of the ceremony, the queue would not be allowed to get any longer than 16 kilometres and has warned mourners of an estimated 30-hour overnight wait to get to Westminster Hall.
The 24-hour round-the-clock process will remain open to the public until 6.30am local time on Monday, just hours before the funeral ceremony for Britain's longest-reigning monarch at Westminster Abbey at 11 am.
The BBC has been live streaming the Lying-in-State, which involves mourners from around the UK and even different parts of the world join a swiftly moving queue to walk through the hall, some pausing very briefly at the side of the coffin in reflection or in prayer.
Members of the royal family had private time with the coffin overnight on Tuesday, when the Queen spent her final night at her London residence of Buckingham Palace.
On Wednesday afternoon, her coffin was taken on a horse-drawn gun carriage through central London in a procession that included King Charles III, his sons William and Harry and the late monarch's other children Princess Anne and Princes Andrew and Edward.
Thousands flocked the route to observe the procession, which was accompanied by gun salutes and Big Ben chimes. Large screens had been set up in Hyde Park for those unable to gain access to the viewing spots along the procession route.