Royal staff have been sending extra supplies to the hospital where the Duchess of Cambridge is in labour as the world awaits a new heir to the throne.
Kate, who is thought to be more than a week past her due date, was taken through a side entrance of St Mary's Hospital in London just before 6am.
The Duke of Cambridge travelled with her by car from Kensington Palace, where she went into labour naturally after spending the weekend there.
She plans to have a normal birth at the hospital's private Lindo wing and the couple's spokesman said: "Things are progressing as normal."
Crowds await the official announcement at Buckingham Palace
Sky News' Royal Correspondent Paul Harrison said it was believed a number of "bits and bobs" had been brought to the Duchess by staff via side entrances at around lunchtime.
It appears officials staged a "dummy run" in preparation for her arrival amid reports of police activity at the hospital last night.
Further officially confirmed details are likely to be thin on the ground until the Royal baby is born.
The arrival will be announced in traditional fashion, with a notice on an easel behind the iron railings of Buckingham Palace.
There is a robust police presence at the hospital
The brief bulletin, on headed Palace notepaper, confirms the sex of the baby but usually gives little else away other than that the baby has been "safely delivered" and perhaps the weight.
Well-wishers from around the globe have descended on the Palace on the off-chance of catching a glimpse.
Larissa Milare, 25, from Sao Paulo in Brazil, said she was keen to see the announcement for herself. "It would be so special," she said. "I don't want to miss this."
Royal fans have also gathered around the hospital, where there is a strong police presence.
Terry Hutt is among the royal fans outside the hospital. Pic: Kat Higgins
Among them is Terry Hutt, 78, from Cambridge, who has been sleeping at the scene for days and is wearing a Union flag suit and tie for the occasion.
The former soldier, who served with the Royal Ordnance Corps, said: "I have lost my voice with all the excitement.
"The health of the baby, and Kate, is the only important element."
Residents from Kate's home village of Bucklebury have spoken of their excitement, with bunting out and pubs that normally shut on a Monday preparing to open when the announcement is made.
The Duchess' former music teacher, Daniel Nicholls, said: "Once the baby is born, Bucklebury will take it in its stride that the future, future King or Queen of England will come from here."
Kate is being tended by a top medical team led by the Queen's former gynaecologist Marcus Setchell, who delivered the Countess of Wessex's two children.
Former midwife Clare Byam-Cook told Sky News: "They'll be monitoring her very carefully to check that the baby is doing well."
Kate's due date has never been announced, but it was widely believed to be July 13.
The world's press have been outside St Mary's, in Paddington, for days in anticipation of the birth.
Some 250 reporters and crew are packed into a relatively small stretch of the street opposite the hospital. Their patch shrunk even further earlier when "twitchy" police herded them from the road to the pavement.
Earlier, Prime Minister David Cameron sent his "best wishes" to the couple, saying: "It is an exciting occasion and the whole country is excited with them, so everyone's hoping for the best."
The 'Great Kate Wait', as it was dubbed by the press, is reaching an end
Others voicing their support included the Archbishop of Canterbury, the Most Rev Justin Welby, who tweeted: "My thoughts and prayers are with Kate and the whole family on this enormously special day."
Celebrities including Joan Collins, Girls Aloud singer Cheryl Cole and ex-Spice Girl Melanie Brown are among those sharing the nation's excitement.
Prince Charles, who is on a two-day visit to Yorkshire, told Sky News at York's National Railway Museum earlier that he knew "absolutely nothing" about his first grandchild's impending arrival.
At York Minster, members of the public shouted "Congratulations" to Charles, who walked over to one woman, smiling, and said: "Do you know something I don't?"
The news that the Duchess was in labour at the Lindo wing - on what is set to be the hottest day of the year so far - was confirmed in a brief statement from Kensington Palace at 7.30am.
The '82 scene at St Mary's for William's birth, left, and a shot from today
The Duke and his younger brother Prince Harry were born in the same wing and the Prince and Princess of Wales famously posed on the building's steps in 1982 holding baby William.
Baby deliveries at the wing start at £5,000, while consultant fees and other charges can bring the cost of a two-night stay to more than £12,000. Its other current patients include the pregnant sister of adventurer Ben Fogle, Tamara.
William is known to want a daughter, while the Duchess is hoping for a son.
Betting on the name of their first-born, which will be third-in-line to the throne, has produced one favourite with a number of bookies - Alexandra. According to Oddschecker.com, George and James are the joint top contenders for a boy.
Kate is thought to be more than a week past her due date
Whatever name the couple go with, it is likely to set a trend for the next generation of infants.
Recent changes to the rules of succession mean that if it is a girl, she will not be leapfrogged to the throne by a younger brother.
The Queen will be informed of the birth in a phone call from William, according to the Queen's former press secretary Dickie Arbiter.
But he said the Royal Family will not visit because it demands an extra level of security. "The last thing they'll want is to disrupt the hospital," he said.
William is at his wife's side
The birth will be a historic first with three heirs in waiting while the sovereign is fit and well, Mr Arbiter added.
Prince William will be on paternity leave from his job as an RAF search and rescue helicopter pilot for two weeks. It is not known how long Kate intends to put her Royal duties on hold so she can devote her time to the baby.
They are becoming parents more than two years after they were married at Westminster Abbey in April 2011, with the celebrations watched by millions around the world.
Doctors say the Royal Family could have its newest member by midnight - the average length of labour for a first-time mother is 12 hours.