The parents of the Duchess of Cambridge are visiting their new Royal grandson in hospital.
The news of the visit by Carole and Michael Middleton came as it was revealed Kate and her newborn son were not expected to leave hospital until later tonight or tomorrow morning.
Crowds are gathered outside St Mary's Hospital in London in anticipation of the departure while the world's media are waiting with cameras at the ready to snap the first pictures of the third in line to the throne.
Sky News Royal Correspondent Paul Harrison said: "We understand that the Duke and Duchess will depart either later this evening, not before 6pm, or tomorrow morning."
Rumours that Kate's hairdresser had arrived at the hospital this morning had earlier sparked rumours that the couple were preparing to take their newborn home to Kensington Palace, but Royal officials dismissed such reports.
Harrison said the longer-than-anticipated stay in hospital's Lindo Wing raised the prospect of visitors, with family members eager to meet the new baby.
He suggested it was a "distinct possibility" that members of the Middleton family - either Kate's mother and father or her brother or sister - would pay a visit.
He said it was unlikely the child's paternal grandfather, Prince Charles, would visit his first grandson today because he is carrying out a Royal engagement in Yorkshire with the Duchess of Cornwall.
The news of their later-than-expected departure came as the Duke and Duchess of Cambridge issued a statement thanking the hospital where their baby boy was born for the "tremendous care" they received.
The Royal couple said: "We would like to thank the staff at the Lindo Wing and the whole hospital for the tremendous care the three of us have received.
"We know it has been a very busy period for the hospital and we would like to thank everyone - staff, patients and visitors - for their understanding during this time."
A Kensington Palace spokesman added: "Mother, son and father are all doing well this morning."
The new parents have also pledged support for a charity supporting St Mary's Hospital in celebration of their son's birth.
They are backing Imperial College Healthcare Charity, which raises money for research and studies designed to improve services to St Mary's and four other hospitals constituting Imperial College Healthcare NHS Trust.
The Royal baby boy, whose name has not yet been revealed, was born at 4.24pm on Monday, weighing 8lb 6oz (3.798kg).
Prince William was at his wife's bedside during her labour. The Duchess spent the night in hospital, as did her husband.
When the new family of three do leave, is is not yet known how the first-time parents will negotiate putting their newborn into a car seat, as required by law.
No such legislation existed when Prince Charles and Princess Diana left the hospital in 1982 after the birth of Prince William.
The Prince of Wales today said he was "thrilled and very excited" about the birth of his first grandchild.
He and the Duchess of Cornwall were met by cheering crowds of well-wishers on a visit to East Yorkshire.
Villager after villager offered Charles and Camilla their congratulations as the royal couple walked around the green in Bugthorpe, which was decked out with Union flags and bunting for the visit.
Many people asked whether the new baby had a name, but Charles gave little away.
One member of the crowd, Alec Dale, said to him as he passed: "We popped a bottle of bubbly last night at our house. I hope you did too."
To this, the Prince replied: "Yes. But just a little bit."
Camilla told the BBC that Charles was "brilliant with children so he'll have a wonderful time".
Later, the Duchess of Cornwall enjoyed a lunch of fish and chips in Bridlington.
She said: "I think these are celebration fish and chips. Celebrating the birth of the new baby."
Chip shop owner John Hutchinson said: "Sue, my other half, tried to prise the name out of her but she wasn't having any of it."
Meanwhile, anyone who is eager to see the easel displaying the official Royal birth announcement outside Buckingham Palace only has a few hours left to do so.
Officials said it will be on show on the forecourt for about 24 hours after confirmation of the birth, meaning is is likely to be removed soon after 8pm tonight.
Many people told Sky News they had come before work as they expect larger crowds later.
Kashmira, 31 and from Hertfordshire, told Sky News: "I didn't really want to come last night when it was so hot but it's such a historical event I couldn't not come."
Lauren, 27, from Surrey, said she popped by on her way to the office, adding: "It's a pretty prestigious event so I dashed here before work. It's so exciting."
Police and security have been putting up barriers to keep the queue orderly.
The jubilation of last night has died down but hundreds of people, from all over the world, still want their slice of the Royal baby excitement.
The Weiner family from Los Angeles, US, told Sky News that they were glad their holiday to the UK coincided with the baby news.
They said they came to the Palace to take a photo of the announcement because "it's a once-in-a-lifetime opportunity".
There is also great anticipation surrounding the name of the new third in line to the throne, who will be known as the Prince of Cambridge.
The Duke and Duchess of Cambridge did not find out if their baby was going to be a boy or girl prior to the birth, meaning they are believed to have considered a stock of names for a future monarch of either sex.
George, James, Alexander, Louis and Henry are currently among the favourites at the bookmakers.
The Queen will be informed of the baby's name before it is announced, which may even be weeks away.
The Queen and Duke of Edinburgh were said to be "delighted at the news".
William's uncle and brother of the late Princess Diana also described his joy at the new Royal baby.
Earl Spencer said: "We're all so pleased: it's wonderful news.
"My father always told us how Diana was born on just such a blisteringly hot day, at Sandringham, in July 1961. It's another very happy summer's day, half a century on."