Jamie Oliver proudly showed off his first son and said he was "shocked" to have a little boy.
His wife Jools gave birth to Buddy Bear Maurice at 6.10pm on Wednesday after what she described as a "hard and fast labour".
The celebrity chef said his family was now complete as he stood with his four children and wife outside the Portland Hospital in central London.
Asked how he had chosen his son's name, he pointed to his wife, who shrugged her shoulders and said: "I just like the name Buddy, I thought it was sweet."
He was given the name Maurice after Jools' late father, who died in 1997 after a stroke.
The unusual choice of name is in keeping with family tradition. Buddy's older sisters are Poppy Honey, eight, Daisy Boo, seven, and 18-month-old Petal Blossom Rainbow.
While the girls appeared delighted with their baby brother, Jamie admitted he was shocked to have had a boy.
Kissing his son on the head, he said: "I never thought for a moment I would have a boy. All you can ever dream of is having a healthy child and that's the best thing in the world. In a way it would have been easier to have had a girl. We're not prepared for a boy - there's no blue in the house.
"When I saw the crown jewels it was a big shock. It's really nice to have a boy."
Asked if he hoped the baby would follow in his culinary footsteps, he said: "I don't know. I'm not going to push him into it. My dad didn't push me."