The Duke and Duchess of Cambridge have welcomed a new baby boy to their family.
Kate, 36, gave birth to the baby at the exclusive Lindo Wing at St Mary's Hospital in Paddington, Lodon.
As the royal baby arrived into the world, crowds of well-wishers waited outside the maternity unit, holding banners and Union flags.
The child, who is a younger sibling to Kate's two older children, George, four, and two-year-old Charlotte, is now fifth in line to the throne.
He is the Queen and the Duke of Edinburgh's sixth great-grandchild.
The 'Great Kate Wait' had officially begun this morning, after Kensington Palace announced the Duchess had been admitted to hospital in labour.
The birth of her third child - which comes as the country celebrates patriotic St George's Day - was confirmed by Kensington Palace via Twitter.
It was also due to be marked with a traditional bulletin on show at Buckingham Palace, as well as a 41-gun salute in Green Park or Hyde Park.
A 62-gun salute at the Tower of London is also set to take place.
Although the wait for the baby's birth may be over, the public could be left guessing as to the youngster's name for several days.
The names given to royal babies are not usually revealed straight away.
Indeed, Kate and husband William, 35, took two days to announce both George and Charlotte's names, informing the Queen of their choice beforehand.
The couple had travelled by car from Kensington Palace to the Lindo Wing earlier today, with the Duchess in the "early stages of labour".
Kensington Palace said in a statement this morning: "Her Royal Highness The Duchess of Cambridge was admitted to St Mary's Hospital, Paddington, London, earlier this morning 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 has been in the care of consultant obstetrician Guy Thorpe-Beeston, who is the surgeon-gynaecologist to the household, and consultant gynaecologist Alan Farthing, the Queen's surgeon-gynaecologist - part of the trusted team who delivered George and Charlotte.
Highly-trained midwives were also on hand as she gave birth, while experts were likely waiting in the wings in case of an emergency.
For her previous births, the Duchess had a 23-strong team of top medics working or on stand-by from Imperial College Healthcare NHS Trust - which runs St Mary's Hospital.
Theatre staff were ready, along with a lab technician, replacement anaesthetists and paediatricians, a back-up for the consultant, and workers from a special baby care unit.
With George, she gave birth 10-and-a-half hours after being admitted to hospital. Meanwhile, Charlotte was delivered just two hours and 34 minutes after her mum arrived at the Lindo Wing.
Just like with her older children, Kate had been hoping for a natural birth and didn't know whether she was having a boy or a girl.
Kate's third child just missed arriving on the Queen's 92nd birthday which was on Saturday. His delivery comes just days before the Duke and Duchess's seventh wedding anniversary, which is on April 29.
There had been speculation that Kate would choose to give birth at home, the norm for generations of royal mothers, after two problem-free labours.
But she eventually decided to return to the Lindo Wing.
She and William had chosen not to know the sex of their new baby – a pattern they have followed throughout all three pregnancies.
There had been other less pleasant similarities, with the Duchess once again suffering from the extreme form of morning sickness, hyperemesis gravidarum.
She undertook her last official engagement on March 22, while heavily pregnant with her third child, before going on maternity leave.
Chic in a £600 cream coat from Goat and a top from high street favourite Hobbs, the future Queen looked relaxed and glowing ahead of the birth.
Kate is due to attend the wedding of brother-in-law Prince Harry to American actress Meghan Markle in Windsor on May 19.
George and Charlotte are expected to have a starring role.
Kate and William met in 2001 when they were at the University of St Andrews, in Scotland. They dated for 10 years and got engaged in Kenya in October 2010.
Their lavish wedding at Westminster Abbey in April 2011 was watched by millions around the world and revitalised a monarchy dogged by scandal and haunted by the spectre of William's mother, Diana.
Kate was young, fresh and from a family who provided the stability that both her husband, now 35, and his brother Harry had lacked.
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The couple's first child George Alexander Louis was born in July 2013 after a difficult pregnancy. The Duchess had suffered deeply debilitating morning sickness which had left her hospitalised.
The Cambridges' second child Charlotte Elizabeth Diana was born in May 2015.
Her name is a tribute to grandfather Prince Charles, the Queen, Kate's great-grandmother (also Elizabeth) and William's mother, the late Princess of Wales.
It is understood Kate was taken to the Lindo Wing before 6am today for the birth of her and William's third child.
The new arrival's home will be a lavish 22-room apartment at Kensington Palace which was extensively refurbished to the couple's specifications.
