"We could not be happier," said the Duke of Cambridge in reference to the new Prince of Cambridge, whose name is yet to be announced to the world. (Agencies)
31-year-old William is on a two-week paternity leave from his job as a Royal Air Force pilot based in Anglesey in Wales to spend time with his new-born.
He spent the night at the Lindo Wing of St Mary's Hospital in Paddington, central London, where the 8lbs 6oz baby was born and is expected to pose for photographs with mother and child on the steps of the hospital later on Tuesday.
After what was labeled as the 'Great Kate Wait' is over, the media speculation is now centered around not only the name of the third in line to Britain's throne but also how he would be secured into a child seat for his journey from the hospital to home, expected to be an apartment in his great-grandmother Queen Elizabeth II's Buckingham Palace.
Child seats are now required by law in Britain, something that did not exist back in 1982 when William was transported from the same hospital after the customary photograph on the steps with mum Princess Diana and dad Prince Charles.
The birth after more than 10 hours of labour brought relief not only to the nation but also the rows of television news anchors camped on the pavement outside the Lindo Wing for days.
Under the blistering heat of the hottest July day in London since 2006, representatives of 150 television stations and some 300 photographers broke into cheers as the official announcement was made yesterday evening.
Crowds remain outside the hospital as well as Buckingham Palace in anticipation and the world's media are still waiting with cameras at the ready to snap the first pictures of the royal heir. "James" and "George" are now the bookies' favourite for the royal baby name.
The arrival of a boy postpones for another generation any anti-sexist statement that a daughter to William and Catherine would have made by overturning the rule of primogeniture. Meanwhile, celebrations carried on across Britain with church bells and gun salutes.
Trafalgar Square in London will be lit blue for a week and the traditional Guard of Honour at Buckingham Palace played "Congratulations" to mark the birth this morning.
"We could not be happier," said the Duke of Cambridge in reference to the new Prince of Cambridge, whose name is yet to be announced to the world.