Prince William and his wife Kate left hospital on Tuesday and gave the world its first glimpse of their baby boy, who becomes third in line to the British throne.
After posing for pictures for the world's media, the couple said they were still working on a name for their son and were feeling "very emotional".
Kate, wearing a blue polka-dot dress, smiled and waved at the cheering crowds as she held her baby, who was wrapped in a white blanket. [embedgallery id=189762]
"We're here to witness history, where a future monarch has been born. I just can't wait to see them today," said Maria Scott, a housewife from Newcastle in northern England who has camped outside the hospital since Saturday.
Kate, 31, gave birth to the couple's first child, who is third in line to the British throne, on Monday afternoon, ending weeks of feverish anticipation about the arrival.
Royal aides said the couple and their newborn are all doing well.
The baby's name will be announced later. George and James, both traditional royal names, were favored choices with British bookmakers for the child who is destined to be king one day.
Kate's parents, Carole and Michael Middleton, gave no clues about the name when they became the first visitors to see the royal couple and their new child in hospital on Tuesday.
Asked if she would reveal the baby's name, Carole Middleton laughed and said: "Absolutely not."
"He is absolutely beautiful," she told the ranks of reporters after their visit, adding that Kate and William were "both doing really well".
Kensington Palace announced the arrival of the boy, weighing 8 lb 6 oz (3.8 kg) at about 8:30 p.m., on Monday, four hours after his birth, saying Kate and her child were doing well and would remain in hospital overnight.
William, who said he and Kate could not be happier, was with them.
Their son is third in line to the throne after grandfather Charles and William, 31, and pushes the fun-loving Prince Harry, William's brother, into fourth place.
"I'm thrilled and very excited," said Charles during an official visit to northern England.
His second wife, Camilla, said: "I think mother, son and father are all well. And I think it's a wonderfully uplifting moment for the country," adding that Charles would make a "brilliant" grandfather.
Congratulations flooded in from around the world after the announcement of the birth, which was followed moment-by-moment by global media as well as TV and press in Britain.
British tabloid newspaper the Sun temporarily renamed itself the Son in honor of the baby and most newspapers issued special supplements. Three trumpeted the banner headline "It's a Boy".
The birth fuels a new wave of popularity for the House of Windsor led by the younger royals, William and Harry, who were both born to Diana at St Mary's Hospital.
Support for the royals dipped after Diana's death in a car crash in Paris in 1997, a year after her divorce from Charles, as the royals were accused of being out of touch with modern Britain over their handling of the aftermath.
But last year's celebrations of Queen Elizabeth's 60th year on the throne showed support for the monarchy was running at a record high.
Hordes of TV crews and photographers, and royal fans wrapped in Union Jack flags, remained camped outside the hospital, waiting for the first photo of the baby, who will be called the Prince of Cambridge.
To mark the birth, the Royal Artillery unleashed a 41-gun salute at London's Green Park and 62 rounds were fired at the Tower of London. Bells at Westminster Abbey, where the couple were married in April 2011, rang out for more than three hours.
Outside the Queen's Buckingham Palace London residence, a military band played "Congratulations" following the traditional Changing of the Guard ceremony.
William and Kate, who met when they were students at St Andrews University in Scotland about 10 years ago, have officially been known as the Duke and Duchess of Cambridge since their sumptuous wedding.
The couple, who have been living in a cottage in north Wales where William is based as a Royal Air Force helicopter pilot, will eventually take up residence with their baby at Apartment 1A at London's Kensington Palace, William's childhood home, when a one million pound refurbishment is completed later this year.
Royal experts said after they leave the hospital, the new prince will be taken out of the public glare.
"All we will probably see is a glimpse of the top of the baby's head," said Joe Little, managing editor of Majesty magazine.
"After that we won't see them for some time. Having a baby is a very private moment and they are a private couple so the next time we see the baby will be the official photo and that could be weeks."
Not all Britons were celebrating the news however. Britain's small Republican movement said it was wrong the future head of state should be chosen by birth.
"Storms over London. God must be unhappy with media coverage too," the campaign group Republic tweeted as sweltering London was hit by a heavy downpour of rain.