Boris and Carrie Johnson are expecting their second baby, they have announced.
Mrs Johnson also revealed on her Instagram account that she suffered a miscarriage earlier this year.
The couple's first child, Wilfred Lawrie Nicholas Johnson, was born in May last year at University College Hospital in London.. Mrs Johnson published a picture of herself cradling the newborn on her social media.
Wilfred is the name of Mr Johnson's grandfather and Lawrie is the name of Mrs Johnson's grandfather, she revealed.
Mr and Mrs Johnson were the first unmarried couple to move into Downing Street together.
Wilfred was the third baby born to a serving prime minister in recent history.
Tony Blair's wife Cherie gave birth to son Leo in May 2000, three years after her husband's first election victory, and David Cameron and wife Samantha welcomed daughter Florence in 2010.
This is a breaking news story. More to follow.