British Prime Minister Boris Johnson was back at work at his Downing Street office after being present while his fiancée Carrie Symonds gave birth to their son, his political spokesman said yesterday.
"The birth took place at an NHS hospital in London and the PM was present throughout," the spokesman said, declining to give more details.
"The PM was with Ms Symonds this morning for the birth of their son and is now back at work in Number 10."
Both mother and baby were said to be "doing very well".
Downing Street said the prime minister, who is currently grappling with the coronavirus crisis, would take a "short period" of paternity leave later in the year.
New fathers in the UK are entitled to up to two weeks of statutory paternity leave.
Mr Johnson returned to work in Number 10 following the birth, but missed prime minister's questions in the House of Commons. He spoke to Labour leader Keir Starmer later yesterday afternoon.
The new family are planning to live in their Downing Street flat along with their dog Dilyn, the spokesman confirmed.
Downing Street declined to say whether the baby was born prematurely and the spokesman was also unable to provide details of the weight, timing, or location of the birth.
The birth was announced shortly before 10am yesterday. The baby's name is not yet known.
The news comes just weeks after Mr Johnson (55) was discharged from intensive care where he had been battling coronavirus. Ms Symonds (32) also suffered symptoms.
She returned to Downing Street after joining Mr Johnson as he convalesced at his country residence, Chequers.
The prime minister's father, Stanley Johnson, said he was "absolutely delighted" and "thrilled" by the birth.
Queen Elizabeth sent a private message of good wishes to congratulate the couple on the birth of their son, Buckingham Palace said.
Mr Starmer said it was "wonderful news" as he, along with many others from the world of politics, congratulated the couple on Twitter.
Conservative former prime minister David Cameron sent his "heartfelt congratulations", and said: "Sam and I are thrilled for you both! Sorry we didn't leave the cot - but the climbing frame should still be in the garden!"
The couple announced in February they were expecting a baby in "early summer" and that they had become engaged at the end of last year.
They made history as the first unmarried couple to officially live together in Downing Street when they moved in last summer.
The new arrival is the third baby born to a serving prime minister in recent UK history.
The baby is Ms Symonds's first child, while Mr Johnson is known to have fathered five others.
In 2013, when Mr Johnson was mayor of London, appeal court judges ruled that the public had the right to know he had an extra-marital affair with a woman who gave birth to his daughter. His previous marriage was to Marina Wheeler, a lawyer.
They had four children together but announced in September 2018 that they had separated. They divorced earlier this year.