The Duchess of Cambridge has been admitted to hospital and is in the early stages of labour, Kensington Palace has said, BBC reports.
She travelled by car from the palace to St Mary’s in Paddington, west London, with her husband the Duke of Cambridge.
The couple do not know the sex of their first child, who will be third in line to the throne.
The world’s press have been camped outside St Mary’s for days in anticipation of the birth. The due date had never been officially announced but had widely been expected to be mid-July.
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.
The Duke of Cambridge has been with his wife on annual leave and will have two weeks’ paternity leave.
It is believed the next time the couple will be seen in public is when they appear on the steps of the hospital with their baby.
The Queen, senior members of the Royal Family, and the duchess’s family – if they are not at the hospital – will be told about the birth first.
Then a royal aide will take the bulletin, signed by key medical staff, from the hospital to the palace under police escort.
After the note is displayed, an announcement will be posted on Twitter and Facebook, and the media will be informed.
