Kate Middleton, the Duchess of Cambridge, has gone into labour and is expecting her first child with Prince William, the Duke of Cambridge.
The Duchess is due to give birth to the boy or girl at the £6,265-a-night private Lindo wing of the of St Mary's Hospital in London.
The couple's spokesman said on the morning Kate went into the early stages of labour: "Things are progressing as normal."
When the royal baby is born, it will be the third in line to the throne, bumping Prince Harry down to fourth. He or she will be the 43rd monarch since William the Conqueror in 1066.
St Mary's said in a statement: "The hospital is delighted that the Duke and Duchess of Cambridge have chosen to have their baby at the Lindo Wing at St Mary's.
"Everyone at the trust is exceptionally proud that this historic moment is happening here."
As the royal couple await the birth of thirst child in their second year of marriage, here are some highlights of their lives and of the royal pregnancy:
September 2001: Prince William and Kate Middleton meet for the first time at St Andrews University where they are both studying art history.
Christmas 2003: The pair reportedly become a couple after living together with two friends. In March they are pictured together on a skiing holiday in Switzerland.
16 November 2010: William and Kate's engagement is announced by Clarence House officials. The prince proposed to Kate while on a private holiday to Kenya in October.
29 April 2011: The pair get married in an extravagant ceremony at London's Westminster Abbey watched by millions around the world. William is made the Duke of Cambridge and Kate becomes the Duchess.
3 December 2012: Buckingham Palace announces that Kate is pregnant but is soon treated in hospital for acute morning sickness. The Palace later announces that the bay is due in July.
5 March 2013: Kate apparently lets slip that she is expecting a daughter on a solo visit to Grimsby. Accepting a teddy bear from a member of the public, she apparently replies: "Oh, is this for our dau...? Thank you so much."
17 March 2013: Kate tells a soldier at a St Patrick's Day parade that they do not know the sex of the child, but says she would like a boy and William a girl.
20 March, 2013: Kate given a "Baby on board" badge when she joins the Queen and Prince Philip at Baker Street underground station to mark the 150th anniversary of the Tube.
4 June, 2013: William and Kate return to their wedding venue at Westminster Abbey when they join the royal family for a service marking the 60th anniversary of the Queen's Coronation at Westminster Abbey.
13 June, 2013: Kate embarks on her final solo engagement before going on maternity leave when she names a new cruise liner - the Royal Princess - in Southampton.
15 June, 2015: The Duchess makes her last scheduled public appearance before the birth at the Trooping the Colour parade.
19 June, 2013: It is confirmed Kate is planning to give birth at the private Lindo Wing of St. Mary's Hospital in Paddington, where Princess Diana gave birth to William and Prince Harry.
22 June, 2013: Kate arrives at St Mary's as she enters the first stages of labour.