Duchess Kate of Cambridge gave birth Monday to a new little prince of Cambridge after several hours of labor and the usual gathering of the media outside St. Mary's Hospital in London.

Shortly before 6 p.m. local time, she and Prince William emerged from the hospital, baby in her arms. She was wearing a knee-length red dress with a white bib collar, and showed only a slight remaining baby bump. Later, they went back inside briefly, then reemerged holding hands, with Will carrying the baby in a carrier.

She was admitted to St. Mary's early Monday in the "early stages of labor," Kensington Palace said in a statement. One minute after 11 a.m. local time (6 a.m. ET), she gave birth to her third royal baby, who weighed 8 pounds, 7 ounces, the palace said in a statement.

Prince William was there for the birth. The baby, whose name the palace has not yet announced, was born on St. George's Day, marking England's patron saint.

After the birth was announced Will emerged about 11:15 a.m. ET and a half-hour later returned with his two older children, Prince George, dressed in his school uniform, and Princess Charlotte, who was wearing one of her trademark flowered dresses.

She waved and smiled at the crowd of cameras, but little George kept his eyes on the ground as they entered the hospital. Will drove himself and his children in a blue Land Rover Discovery. The children were later returned to Kensington Palace

The former Kate Middleton, 36, and Prince William, Duke of Cambridge, 35, arrived at the Lindo Wing at St Mary's Hospital, in London's Paddington neighborhood, by car.

The baby, the royal couple's third, is grandmother Queen Elizabeth II's sixth great-grandchild and become fifth in line to the throne.

He will join sister Princess Charlotte, 2, and Prince George, 4, in the growing Cambridge family, as the third grandchild of Charles, Prince of Wales, and his late first wife, Princess Diana.

As with her previous pregnancies, Will and Kate did not know the sex of the baby beforehand, palace officials confirmed in a briefing weeks before the birth.

The palace did not immediately announce the new prince's name. Among the names favored by British bookmakers for a boy: Albert, Arthur, Frederick, James and Philip.

The little prince is a historic royal baby: Unlike previous princes born in the United Kingdom, he will not automatically displace his older sister, Princess Charlotte, 2, in the line of succession.

Shortly before older brother George was born, British law changed to make birth order the determining factor in succession, replacing gender — male primogeniture — as the default rule that developed over 10 centuries.

Aware that a 300-year-old set of laws then governing the succession looked increasingly egregious and inexplicable in the 21st century, British lawmakers decided the time for "royal equality" had finally arrived.

The newest little royal will displace Uncle Prince Harry, 33, in the succession; he will move down to sixth in line, and any children he has will follow him.

As per previous royal births, great-granny the queen was first to be notified. Members of both families have been notified and expressed delight, the palace said.

Then, in keeping with a 181-year-old tradition, a statement was posted on an easel in the forecourt of Buckingham Palace, just as it was after George and Charlotte's births. Bells will toll and a gun-salute was set to start booming.

Now that the third Cambridge baby has arrived, attention will turn to Harry's upcoming wedding to American actress Meghan Markle, 36, at Windsor Castle on May 19. The other four Cambridges — his brother Will, sister-in-law Kate, nephew George and niece Charlotte — are expected to be there and play roles (Will as Harry's likely best man), but probably not the new baby.

Like his siblings, the baby arrived without any medical crisis. The medical team was led by obstetrician Guy Thorpe Beeston and Alan Farthing, surgeon gynecologist to the queen, who also helped deliver the other royal babies.

George, Charlotte and Will and Harry, too, were born in the maternity Lindo Wing of St. Mary's, just a short drive from the Cambridge home at Kensington Palace.

As with Kate's previous pregnancies, a large crowd of reporters, photographers and media cameras gathered in the narrow street across from the door of the Lindo Wing, along with a crowd of ordinary Brits eager to glimpse the latest addition to the royal family.

Barriers for the media pen and parking restrictions on the narrow street went up April 9 in preparation.

A blustery but sunny day in London, the site outside the hospital has been taken over by broadcasters from around the world who mixed with hospital staff, passersby and visitors to London. When the news spread that Duchess Kate gave birth to a healthy baby boy, cheers and brief clapping erupted.

The words "it's a boy" were flashed in lights around the top of London's BT Tower, which can be seen for miles around, the Associated Press reported

“This is really crazy, I can’t believe it. Some of these people have been here for 15 days waiting for this to happen,” said Olivia Dragor, remarking on the chaotic scrum of media, tourists and royal well-wishers outside St. Mary’s in central London.

Dragor, 21, is spending a year abroad studying communications in London. Her home college is the University of Southern California. “We don’t really get this kind of thing back home,” she said, adding that she liked the royal family but is not a full-time devotee.

“It’s wonderful, it’s really nice to see people so happy and excited,” said Lynne Gant, 62, an Australian tourist who was waiting on the perimeter of barricades that had been set up for media here.

Gant said part of her interest in the royal family stemmed from her grandmother, who was British. She added that she hoped to get a glimpse of the Duchess of Cambridge with her new babe in her arms when she leaves the hospital, expected later Monday.

Some Londoners reacted to the news that a new prince had arrived with typical British understatement.

“It’s a good thing, pleased for them, but it’s time to get back to work,” said James Long, 29, an accountant who was passing by the hospital on his lunch break.

Tony Appleton, 82, the "town crier" who showed up in royal-looking regalia for all three of the Cambridge’s babies, said that he wasn’t sure whether he would wait around for Duchess Kate to emerge from the hospital with the new prince.

“It’s not easy doing all this,” he said, pointing to his elaborate dress and robes. Appleton said that he works “under his own steam,” meaning that he does not make the announcements in an any official capacity to the palace or the royal family.

“But my uniform is genuine,” he added. “I had it made specially for the queen’s birthday last year.” Appleton said it cost over four thousand pounds (about $5,500) and he paid for it with his own money.

Prime Minister Theresa May, London Mayor Sadiq Khan and other British politicians and public figures sent their well wishes and congratulations over social media but otherwise did not reflect on the impact for the nation.

British Airways celebrated by arranging for a replica of the royal easel that is placed on the forecourt of Buckingham Palace as formal notice of the birth to be placed in an arrivals hall at Heathrow Airport’s Terminal 5, according to a company statement. For its customers who were up in the air traveling when the announcement was made, cabin crew broke the news over aircraft public announcement systems, the company said.

Kate's other babies had easy deliveries (she gave birth and left the hospital on the same day for Princess Charlotte), in contrast to crippling bouts of acute morning sickness that forced her to cancel engagements and stay in bed in the early stages of her pregnancies. She was so ill she had to miss George's first day of his new school; Will did the solo dropoff instead.

The Cambridges are now full-time royals based in their sprawling 20-room Apartment 1A at Kensington Palace. George's school is just across the Thames River; Charlotte started at a nursery school near the palace in January.

The family also has a country retreat, Anmer Hall, in Norfolk on the queen's Sandringham estate, where they may spend some time post-baby. Will is no longer working part-time in Norfolk as a helicopter rescue pilot and Kate has expanded her royal patronages and engagements to take on more royal duties.