King Charles and his siblings will keep a silent vigil at the coffin of his late mother Queen Elizabeth on Friday night, while thousands of people are standing in line for miles to pay their last respects to the monarch during her lying-in-state.
Charles, his sister Princess Anne, and brothers Princes Andrew and Edward will join the ceremonial guard for the 15-minute vigil at Westminster Hall in central London, where their mother's coffin has rested since Wednesday.
On Saturday evening, Queen Elizabeth's eight grandchildren, including Princes William and Harry, will also stand vigil beside her coffin, a royal spokesman said.
The coffin will lie in state at Westminster Hall in London until the state funeral on Monday to allow members of the public to pay their respects to the late monarch.
Already tens of thousands of people from all walks of life from Britain and around the world have patiently queued for the opportunity to pass by the coffin. By Friday morning, the line stretched back almost 8 km and people were facing a 14-hour wait to reach the hall.
The government said the queue, which snakes along the south side of the River Thames, was close to capacity and that entry may need to be paused.
Officials expect about 750,000 people to view the coffin before the lying-in-state ends at 6.30am on Monday.
Malcolm Keyte, 78, from Surrey in southern England, queued for nearly 10 hours with his two daughters.
"We just want to pay our respects and our thanks," he told Reuters near the front of the queue just after 7am "She was a wonderful lady who served the country very well, very loyally, for very many years and we should all be very grateful," he said.
Before the 7.30pm vigil, Charles and his wife Camilla, the Queen Consort, will travel to Wales.
The trip will mark the end of a tour of the United Kingdom where he has performed ceremonial duties to acknowledge his status as the new monarch and head of state, and to greet the public mourning the loss of Elizabeth, who reigned for 70 years and died last Thursday at the age of 96.
The royal couple will be greeted with a 21-gun salute, attend a cathedral service, and travel to the Welsh parliament. Charles will meet the Welsh first minister and other politicians.
Wales has a particular significance for the new king, who for five decades preceding last week's accession had the title Prince of Wales.
"His passion and affection for Wales has been clear," his spokesman said. "He has shown a life-long commitment to the country's people."
Meanwhile William - Charles' son and the new Prince of Wales - will visit troops from New Zealand, Canada and Australia who are in Britain to take part in events around the state funeral.
He will be accompanied by his wife Kate, the new Princess of Wales. The title was previously held by William's mother Diana, killed in a car crash in 1997.
Diana's death likewise prompted a national outpouring of grief, and William spoke on Thursday of how the solemn events of the last week had revived memories of the funeral procession for Diana.
On Wednesday, William, alongside Charles and his younger brother Harry, walked in a procession behind a gun carriage carrying the queen's coffin from Buckingham Palace to the Palace of Westminster, a scene reminiscent of when, as boys 25 years ago, the princes had followed Diana's casket.
"The walk yesterday was challenging... brought back a few memories," William said as he and Kate spoke to well-wishers and viewed the sea of floral tributes outside the royal residence of Sandringham in eastern England.
In an adjustment to protocol, both Prince Harry and his uncle Prince Andrew will be allowed to wear military uniform when they take their turns standing vigil at the queen's coffin.
The two - though both war veterans - have so far appeared at events in morning suit as they lost their honorary military titles when they stepped back from public royal duties.
Elizabeth's eight grandchildren will keep vigil beside her coffin for 15 minutes on Saturday evening, with William at the head and Harry at the foot, a Kensington Palace spokesman said.
"At the King's request, they will both be in uniform."
Their spouses will not attend the vigil, the spokesman said.
Presidents, prime ministers and royalty from around the world are coming to London for the funeral, which is likely to be one of the grandest ceremonies ever seen in the British capital, involving thousands of military personnel.
"It is our aim and belief that the state funeral and events of the next few days will unite people across the globe," said the Earl Marshal, Edward Fitzalan-Howard, the Duke of Norfolk, who is England's most senior peer and is in charge of state occasions.
London's Heathrow Airport has said it will cancel 15% of its flight schedule on Monday to reduce noise over the British capital and guarantee that the skies will be quiet during a two-minute silence at the end of the funeral.
Monday has been declared a national holiday. Many shops and supermarkets will be closed and a range of other economic activities will grind to a halt. Thousands of people face cancelled doctor appointments or operations.