The Queen's coffin has arrived at Westminster Hall where it will remain on public display for the lying in state until the late monarch's funeral on Monday.
Earlier, the coffin left Buckingham Palace on a horse-drawn gun carriage. King Charles III walked directly behind, flanked by other senior royals including his two sons Prince William and Prince Harry.
The procession route took the coffin from Buckingham Palace through the Queen’s Gardens, up The Mall, along Horse Guards Road and through Horse Guards Arch.
It then turned south at Whitehall, down Parliament Street, through Parliament Square and New Palace Yard to arrive at Westminster Hall — a journey of 2 kilometres.
The coffin was draped in the Royal Standard with the Imperial State Crown placed on top, along with a wreath of flowers.
Unlike the funeral procession in Edinburgh two days ago, Wednesday's event was not silent, with a military band playing funeral marches.
Soldiers in scarlet uniforms led the cortege, with the gun carriage drawn by the King's Troop, Royal Horse Artillery, as it moved slowly through central London.
King Charles III marched with Princess Anne on his left, followed by Prince Andrew and Prince Edward.
Behind them, Prince William walked directly behind his father, with Prince Harry on his left, then Peter Phillips, the son of Princess Anne.
Upon arrival in the medieval Westminster Hall, the coffin was placed onto a raised platform known as a catafalque and topped with the Imperial State Crown, orb and sceptre.
After the coffin was placed on the platform, a 20-minute service was held in Westminster Hall for members of the royal family.
Also in attendance were members of the House of Commons and House of Lords, as well as members of the UK's devolved parliaments in Wales, Scotland and Northern Ireland.
During the service, a choir sang Psalm 139 before Archbishop of Canterbury Justin Welby said a prayer and recited a passage from the Gospel of John.
'We're never going to see anything like it again'
Ahead of the procession, crowds lined major sites across London, including The Mall, Whitehall and the footpaths outside the Palace of Westminster.
King Charles III walked for 40 minutes across London in the afternoon sun, but it was people in the crowd who had been waiting for hours who needed medical attention.
Paramedics assisted several people who collapsed, while police questioned others as part of their huge security operation across the city.
There was a large military presence, with major roads and walkways around Westminster closed.
Most people in the inner city were forced to take long detours throughout the afternoon.
A Buckingham Palace spokesperson said the Queen had three key roles in her life: head of the family, head of the nation and head of state.
Wednesday marked the moment the coffin was passed from the family to the state.
While the love of the monarchy and admiration for Queen Elizabeth II has brought thousands to the streets, there were a lot of people in the crowd on Wednesday who were there to bear witness to history.
"I think this is something that a lot of people in Britain will remember the rest of their lives," Matthew McKenzie, 22, told the ABC.
"I didn't really know what to expect. I mean, the last sovereign that died was in 1952. So, nothing's really going to prepare you for what's to come and what's to follow."
Rebecca Edwards and Steve Croft travelled three hours by car and one hour by train to stand behind the masses of crowds and hold their twins Zara and Evie up as the procession passed. They wanted them to be here.
"It's history, isn't it? We wanted to be here. It's being part of history I think, for me," Ms Edwards said.
It was the same for Debbie and Simon Wright.
"We're never going to see anything like it again in our lifetime, are we? It's literally once in a lifetime," Debbie said.
"It's just so moving. And so brilliant to see so many people out there and the silence was amazing.
"There's a consensus about what to do. We all know how we want to respond. I think it's what the British do really well."
Lying in state begins
Now, another part of this historic ritual begins.
The body of Queen Elizabeth II is lying in state and the doors of Westminster Hall have opened to the public.
Those who have patiently lined up will be able to visit the hall 24 hours a day to pay their respects, right up until the early morning of the Queen's funeral on Monday when she will be moved across the road to Westminster Abbey.
The queue to view the Queen's coffin began moving shortly after the service inside the hall finished.
The government warned the queue could stretch for up to 16 kilometres along the southern bank of the River Thames, winding past landmarks such as the giant London Eye and the reconstruction of Shakespeare's Globe theatre.
In Scotland, about 33,000 people filed past the coffin during the 24 hours it was at St Giles' Cathedral in Edinburgh, but the memorial in London is a much larger occasion.
As many as 750,000 mourners are expected to walk through Westminster Hall to pay their final respects.
ABC/wires
