Louis is a sixth great-grandchild for Queen Elizabeth, who turned 92 on Saturday, and her husband Prince Philip
London (AFP) - Prince Charles voiced his joy Tuesday at the arrival of his third grandchild, as Britain waited to discover what Prince William and his wife Kate will call their new baby son.
Cannons were fired in London to mark the arrival of the little prince, who is fifth in line to the throne, and the bells of Westminster Abbey rang out in celebration.
The boy, weighing eight pounds and seven ounces (3.8 kilogrammes), was born at 11:01 am (1001 GMT) on Monday with William present for the birth.
The Duke and Duchess of Cambridge left St. Mary's Hospital in London around seven hours later, showing off their baby to the world's media and royal fanatics camped outside.
William's 69-year-old father Charles, the heir to the throne, said he and his wife Camilla were thrilled to have a new addition to the family.
The new baby is the younger brother of William and Kate's children Prince George, four, and two-year-old Princess Charlotte.
"We are both so pleased at the news," Charles said in a statement.
"It is a great joy to have another grandchild. The only trouble is I don't know how I am going to keep up with them."
William, 35, and 36-year-old Kate are back at their Kensington Palace home in London.
As he left the hospital on Monday, the duke told reporters he was "very happy, very delighted," adding: "Thrice the worry now."
- Baby name speculation -
Kensington Palace said the baby's name would be announced "in due course".
Betting shops had Arthur as their favourite, followed by James, Albert, Philip, Alexander, Henry and Michael.
"Arthur is the hot favourite at the moment," said Harry Aitkenhead, spokesman for bookmakers Coral.
"James, Albert and Philip have also been backed and anything else would be a major shock."
Jessica Bridge of Ladbrokes said: "Arthur might be the favourite with the bookies, but it's actually James that's the favourite with punters."
Official commemorative souvenirs are already on sale, despite the prince's name being unknown.
The Royal Collection china is decorated with gold ribbons, silver pompoms and a coronet-inspired pattern.
The plates and pillboxes bear the words: "Welcome to our new royal baby."
The birth was marked Tuesday by bell ringing at London's Westminster Abbey, where William and Kate were married in 2011 in a ceremony watched by up to two billion people worldwide.
They rang "a full peal of Cambridge Surprise Royal", the abbey said.
The birth was also to be celebrated with a 41-gun salute in London's Hyde Park, while 62 rounds were fired near the Tower of London.
Britain's overseas territories were also celebrating, with a 21-gun salute due to be fired in Gibraltar and a single round gun salute and rifle volley planned in Bermuda.