Carrie Symonds, fiancee of British Prime Boris Johnson, gave birth to a healthy baby on Wednesday.
The delivery at a London hospital was slightly earlier than had been expected.
The 32-year-old had previously said her baby was due in early summer.
It was unclear if Johnson would take paternity leave - given the government is facing the worst health crisis since the 1918 influenza outbreak.
But on the streets of London the birth was welcomed as a rare piece of happy news.
(SOUNDBITE) (English) LONDON RESIDENT, JOAN WATERFIELD, SAYING:
"Congratulations to Boris and Carrie. I just heard it's a little boy and I hope everything's ok."
(SOUNDBITE) (English) LONDON RESIDENT MAX PERCY, SAYING:
"I think it's probably a tough time to be bringing a child into the world but I am really happy for him. He's got a lot on his hands at the minute."
(SOUNDBITE) (English) LONDON RESIDENT JAN HIRST, SAYING;
"I just can't imagine what it's like for him and one can only hope that he's getting a lot of support"
The new arrival tops a tumultuous month for Johnson.
He returned to work on Monday after recuperating from COVID-19, which had left him gravely ill in intensive care at the peak of the UK outbreak.
Symonds, a former PR executive, also had virus symptoms but recovered more swiftly.
A wide spectrum of politicians have sent congratulations to the couple - among them finance minister Rishi Sunak and opposition Labour party leader Keir Starmer.