The world is waiting for news of the royal baby after the Duchess of Cambridge was admitted to hospital after going into labour on Monday morning.
Kate and husband William arrived at the private Lindo Wing of St Mary's Hospital in London by car without a police escort just before 6am.
The Duchess had planned for a natural birth and a few hours after she arrived at the private unit in Paddington, Kensington Palace said things were "progressing as normal".
There were no further updates from the Duke and Duchess's household and as the evening goes on, it looked more and more likely that an announcement will not be made until Tuesday.
However, Kensington Palace did reveal that any announcement of the birth would be made through a formal press release - probably by email - instead ofthe traditional manner of a notice outside Bukingham Palace.
That didn't deter the crowds of wellwishers who had gathered outside the Palace during the day with their numbers increasing as the evening went on.
Kate and William are the focus of much of the world's attention
The Prince of Wales, who will become a grandfather for the first time when Kate's baby is born, was quizzed about the birth as he visited the National Railway Museum in York to mark the 75th anniversary of the Mallard locomotive.
But the heir to the throne revealed he was awaiting news like everybody else telling Sky News he knew "Absolutely nothing at the moment, we're waiting".
The Queen was informed about the Duchess being admitted to hospital and this afternoon she returned to Buckingham Palace as planned, after spending the weekend at Windsor Castle.
David Cameron wished the royal couple well telling the BBC: "Best wishes to them, a very exciting occasion and the whole country is excited with them. So, everyone's hoping for the best."
The news that "the Great Kate Wait" - as bored journalists have dubbed their vigil outside the hospital - was finally over was announced in a brief statement from Kensington Palace at 7.30am after rumours began circulating that Kate had been spotted arriving.
The statement read: "Her Royal Highness The Duchess of Cambridge has been admitted this morning to St Mary's Hospital, Paddington, London, in the early stages of labour.
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"The Duchess travelled by car from Kensington Palace to the Lindo Wing at St Mary's Hospital with The Duke of Cambridge."
The Duchess is being tended by a top medical team led by the Queen's gynaecologist Marcus Setchell, who delivered the Countess of Wessex's two children.
Assisting him is Alan Farthing, the former fiance of murdered TV presenter Jill Dando, who is gynaecologist to the royal household.
The world's press have been camped outside St Mary's in Paddington for days in anticipation of the birth and even the Queen has joked about the imminent arrival of the newest member of her family, saying she hoped the baby was born before she went on holiday later this week.
The hospital's Lindo Wing is a private obstetric unit, with prices starting at just under £5,000 for a normal delivery package over 24 hours, with consultants' fees around £6,000 extra depending on the care required.
Wellwishers have been congregating outside Buckingham Palace waiting for the announcement
The Duke and his younger brother, Prince Harry, were born in the Lindo Wing and the Prince and Princess of Wales famously posed on the building's steps in 1982 holding baby William in turn.
William had taken annual leave to be with his wife last week, but is now on two weeks' paternity leave from his job as an RAF search and rescue helicopter pilot.
It is not known how long the Duchess will take off from her royal duties to care for her first child.
The new royal baby will be the Queen's third great-grandchild and is destined to be crowned monarch.
It will be the 43rd sovereign since William the Conqueror if, as expected, it follows reigns by Charles then William.
The royal couple do not know the sex of their baby but the Duke is known to want a daughter while the Duchess is hoping for a son.
Recent changes to the rules of succession mean if a girl is born she will not be leapfrogged by a younger brother at a later date.
The sex of an infant in direct line to the throne no longer determines whether he or she wears the crown.
Betting on the name of the royal baby, which will be third-in-line to the throne, has produced one favourite with a number of bookies - Alexandra.
Many punters believe William and Kate will have a girl and have put their money on the name.
Other monikers that have attracted royal fans include Charlotte, Diana, Elizabeth and Victoria, with George and James picked by those who think the new baby will be a boy.
Soon after the royal couple arrived at the hospital wing a strong police presence was seen around the building with two officers guarding the main entrance.
But among the dozens of broadcasters, photographers and journalists were royal fans who had a ringside view of events.
Carly Gargett, 31, an event manager from Sydney, Australia, who lives in London, visited the hospital on her way to work.
She said: "I don't think I'll be doing a lot of work today, I have the royal baby cam live feed to my phone, I am so excited.
"And Kate is handling it all in such style as always - it can't be easy with the eyes of the world on her."