Edinburgh (AFP) -
Thousands of people queued throughout the night in Edinburgh to pay their respects to Queen Elizabeth II before her coffin was to be flown to London on Tuesday ahead of a state funeral.
Her eldest son and successor, King Charles III, meanwhile jetted to Northern Ireland to meet political and religious leaders before a church service.
Charles, 73, is on a tour of all four nations of the United Kingdom to mark the start of his reign. He is due to visit Wales on Friday before the queen's funeral on September 19.
In Edinburgh on Monday evening, Charles and his three siblings held a 10-minute vigil beside their mother's coffin inside the 12-century Saint Giles' cathedral as members of the public filed past.
Four members of the monarch's Scottish bodyguard, the Royal Company of Archers, stood with their heads bowed at each corner of the oak coffin.
It was draped in the Royal Standard of Scotland and topped with the ancient Crown of Scotland and a wreath including heather from Balmoral, the remote royal retreat where the 96-year-old queen died last Thursday.
Images of the poignant, pomp-filled scene dominated the front pages of Britain's newspapers on Tuesday.
'The Queen's guard,' headlined The Times, alongside a photo of a sombre-looking Charles.
- 'Moment in history' -
Mourners queued for hours to file past the casket through the night. Waiting times were still roughly two hours at around 6:00 am, the Scottish government said.
'It's part of history. We are pensioners... we'll never see this again,' Lynn Templeton, visiting Edinburgh from northwest England, told AFP.
Vicki, 45, took an early train from Glasgow with her nine-year-old son 'just to pay our respects'.
'(It's) just a moment in history, once in a lifetime,' she said.
The queen's only daughter, Princess Anne, will accompany her mother's body later on Tuesday afternoon on the next leg of its journey by Royal Air Force jet to an airfield near London.
The queen will first be driven to Buckingham Palace, then transferred to Westminster Hall on Wednesday, where she will lie in state for four days.
Soldiers from the Household Division of regiments, which form the monarch's bodyguard, began practising for the funeral procession in London overnight Monday to Tuesday.
On Monday, Charles, again flanked by his three siblings, led a procession on foot carrying the queen's body through hushed Edinburgh streets packed with mourners.
The queen's coffin was driven on Sunday to the Scottish capital from Balmoral and stayed overnight at the official royal residence in Scotland, the Palace of Holyroodhouse.
Accompanied by kilted soldiers, the late queen was taken from the royal residence to the cathedral for a prayer service.
Thousands of people lined the route along the city's famous Royal Mile to watch the procession make its way to St Giles', as cannons fired at one-minute intervals from Edinburgh Castle.
The royals were joined by Prime Minister Liz Truss and Scottish First Minister Nicola Sturgeon at the service for the country's longest-serving monarch, who reigned for 70 years.
- 'Heartbreaking' -
In Northern Ireland, people turned out at Hillsborough Castle -- the monarch's official residence there and where Charles will meet the region's political leaders -- to show support.
Flowers, cuddly toys and handwritten notes carpeted the gates of the historic castle grounds, southwest of Belfast.
'This is very important for Charles to come here and be in Royal Hillsborough,' Rhonda Irvine, 47, wedding and events administrator, told AFP, using the village's full title after it was given official royal status last year.
Describing Charles's late mother as an 'inspiration for him', she predicted he would be a 'very good' king.
Ann Sudlow, 61, a retired nurse from nearby Dromore, had also made the early morning drive 'to show the king that we're behind him as a country and Northern Ireland is supporting him'.
While large crowds are expected to welcome Charles, visiting the deeply divided region still scarred by sectarian violence could prove testing.
He will meet Belfast's feuding political leaders -- split between fiercely loyal unionists and nationalists who want to reunify with Ireland -- before attending an Anglican religious service in the city.
The president, prime minister and foreign minister of Ireland are also set to attend.
- 'Unique event' -
Hundreds of thousands of mourners are expected in London to file past the queen's coffin at Westminster. The first arrived for the queue on Monday -- more than 48 hours before the line opens.
It is predicted to snake for several miles (kilometres) along the banks of the River Thames.
'It's going to be emotional,' said Vanessa Nanthakumaran, a 56-year-old administration assistant originally from Sri Lanka.
'It's going to be a once-in-a-lifetime chance to be part of this unique event,' she told AFP.
Britain is in 10 days of national mourning for Elizabeth II, who was a fixture of the nation's life and consciousness for seven decades.
Charles has seen his popularity recover since the death of his former wife Diana in a 1997 car crash. But he has also been embroiled in several scandals in recent years.
With republican movements gaining ground from Australia to the Bahamas, the new king faces a challenge keeping the Commonwealth realms in the royal fold.