The Duchess of Cambridge has been admitted to hospital in the early stages of labour and is "progressing as normal", Kensington Palace has said.
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 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.
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. The Duchess travelled by car from Kensington Palace to the Lindo Wing at St Mary's Hospital with The Duke of Cambridge."
Kate is planning to have a natural birth and a spokesman added that "things are progressing as normal". The Duchess 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. Assisting him is Alan Farthing, the former fiance of murdered TV presenter Jill Dando, who is the Queen's current gynaecologist.
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.
David Cameron told 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 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. Asked by Sky News if he knew anything about the the birth, he replied: "Absolutely nothing at the moment, we're waiting."
Dickie Arbiter, a former press secretary to the Queen, said the birth will be a historic first. "There will be three heirs in waiting while the sovereign is fit and well, and that's a first," he said.
"The Queen will be the first to be informed because William will telephone her as soon as something happens. The Middletons might come down but the royals won't because it demands another level of security and the last thing they'll want is to disrupt the hospital. It doesn't really warrant a visit," he added. "Diana was in for 22 hours; she had the baby one day and left the next. Kate might do the same thing."
