King Charles, his sons Princes William and Harry, and other senior royals joined a solemn procession accompanying Queen Elizabeth's coffin as the late monarch made her final journey from Buckingham Palace on Wednesday.

Huge crowds gathered in central London to witness the queen being taken from the palace to parliament as artillery guns fired salutes and Big Ben tolled, the latest in a series of poignant ceremonies as the nation mourns the queen who died last week aged 96 after seven decades on the throne.

Lying on a gun carriage, covered by the Royal Standard flag and with the Imperial State Crown placed on a cushion on top alongside a wreath of flowers, the coffin bearing Elizabeth's body was taken in a slow, sombre procession from her London home to Westminster Hall. There it will lie in state for four days.

Walking directly behind were Charles and his siblings, Anne, Andrew and Edward.

In a group that followed were Charles's sons Princes William and Harry, a doleful scene reminiscent of when, as boys 25 years ago, they followed the casket of their mother Princess Diana when it was taken on a similar procession through central London.

It was also a symbolic show of unity as William, 40, now the Prince of Wales, and Harry, 37, the Duke of Sussex, are said to be barely be on speaking terms after a bitter falling out in the last couple of years.

"It was very moving, seeing the family. It was a powerful show of unity," said Jenny Frame, 54, who waited for more than four hours to see the procession.

Paul Wiltshire, 65, commented: "I don't think we'll see anything like that again ever, or a queen like that again. An end of an era."

Hushed silence

A military band playing funeral marches and soldiers in ceremonial scarlet uniforms accompanied the gun carriage pulled by the King's Troop, Royal Horse Artillery, as it moved slowly through central London, where many roads were closed to traffic.

Guns fired every minute at Hyde Park, while parliament's famous Big Ben bell also rang at 60-second intervals. The crowds stood in a hushed silence as they watched the procession but then broke into spontaneous applause when it passed. Some threw flowers.

Other senior royals including Charles' wife Camilla, now the Queen Consort, Kate, William's wife and now Princess of Wales, and Harry's wife, Meghan, travelled by car.

When the procession reached Westminster Hall, a medieval building with origins dating back to 1097 and the oldest part of the Palace of Westminster that houses the British parliament, the coffin was carried inside by soldiers from the Grenadier Guards and placed on a catafalque surrounded by candles.

A short service followed, conducted by the Archbishop of Canterbury, the spiritual head of the Anglican Church, as senior politicians watched on. The royals quietly departed, with Harry and Meghan holding hands.

A constant vigil will be held by soldiers in full ceremonial uniforms at the four corners of the catafalque.

Just after 5pm the public began to file past the coffin, some in tears, many bowing their heads. There will be a constant stream of mourners, 24 hours a day, during the four days of lying in state that lasts until the morning of the funeral on Sept 19.

"It was quite overwhelming," said Thomas Hughes, 20, who waited nearly 14 hours with his brother to view the queen lying in state. "When you put yourself through that, and then you get to the moment you're waiting for you are just that little bit more emotional. It's a very powerful thing."

A Buckingham Palace spokesperson said Elizabeth had three keys roles in her life: head of the family, head of the nation, and head of state. Wednesday marked the moment the coffin passed from the family to the state.

Long queue

People started waiting in line late on Tuesday, sleeping on the street in the rain, to be one of the first to file past the coffin. By Wednesday afternoon, the queue was 2.5 miles long.

The government has warned the queue could eventually stretch for up to 10 miles (16km) along the southern bank of the River Thames.

Among those gathered, some were there to represent elderly parents, others to witness history, and many to thank a woman who, having ascended the throne in 1952, was still holding official government meetings just two days before she died.

"She's an icon of icons," mourner Chris Imafidon said. "I must at least endure this camping out of respect."

Speaking to people in the queue, Archbishop of York Stephen Cottrell quipped: "We are honouring two great British traditions - loving the queen and loving a queue."

Elizabeth's coffin was flown back London late on Tuesday from Scotland, where it had been since her death at her Scottish summer holiday home Balmoral Castle.

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.

A senior palace official described Wednesday's poignant pageant as relatively small and personal. The full-scale ceremonial procession on the day of her funeral is likely to be one of the biggest the country has ever witnessed.

Royalty, presidents and other world leaders are expected to attend, although no one from certain nations, such as Russia, Afghanistan, and Syria will be invited.

US President Joe Biden, who has said he will be there, spoke to the new king earlier on Wednesday, the White House said, and "conveyed the great admiration of the American people for the queen".

A spokesperson for the king said he had also completed a series of phone calls to other leaders, including the presidents of Ireland and France and the governors general of Australia, Canada and Jamaica.