Although he and Kate Middleton didn’t answer questions from the media after debuting their newborn son on the steps of the Lindo Wing at St. Mary’s Hospital Monday evening, the royal dad told onlookers that they were “very happy, delighted” about their new addition as he secured his newborn son into his car seat before heading home to Kensington Palace.
Holding up three fingers, William smiled and said, “Thrice worry now.”
The royal baby was introduced to the world just seven hours after Kate gave birth.
“We didn’t keep you waiting too long,” William joked of their quick hospital stay.
Kate looked stunning in a red dress with a white collar (almost identical to the dress Princess Diana wore after giving birth to Prince Harry) by Jenny Packham after a visit from her go-to stylist, Natasha Archer, who was spotted leaving the Lindo Wing an hour before the royal gave birth.
The new baby, whose name has not been announced, had some visitors before leaving the hospital: Big brother Prince George, 4, who was still donning his school uniform, and big sister Princess Charlotte, who turns 3 in May and adorably showed off her royal wave for those gathered.
At a Kensington Palace event in February, William admitted he was catching up on as much sleep as possible before he and Kate welcomed baby No. 3.
“Our third child is due in April, I’m getting as much sleep as I can,” he told one of his guests, to which they replied that he could save time by having twins. William then responded, “Twins? I think my mental health would be tested with twins.”
William then told another guest: “Two is fine — I don’t know how I’m going to cope with three, I’m going to be permanently tired.”
Kensington Palace announced that Kate had given birth on Monday, after she was admitted to the hospital earlier that morning.
“Her Royal Highness The Duchess of Cambridge was safely delivered of a son at 11:01 hours,” the statement said. “The baby weighs 8lbs., 7oz. The Duke of Cambridge was present for the birth.”
“The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall, Prince Harry and members of both families have been informed and are delighted with the news,” the statement continued. “Her Royal Highness and her child are both doing well.”
- Can’t get enough of PEOPLE’s Royals coverage? Sign up for our newsletter to get the latest updates on Kate Middleton, Meghan Markle and more!
For the first time in history, a female royal’s spot in line to the throne won’t be bumped by the arrival of a younger brother. Thanks to the Succession to the Crown Act 2013, birth order determines who will become the next king or queen of the U.K., regardless of gender. Had it not been in place, Charlotte would have lost her spot when Kate gave birth to a boy.
The royal baby remains fifth in line of succession after Prince Charles, Prince William, Prince George and Princess Charlotte.
With his arrival, Prince Harry is now sixth in line, and Prince Andrew, Princess Beatrice and Princess Eugenie will all move down a place in the line of succession with the arrival of William and Kate’s younger son.