Prince William's wife Catherine is normally careful to protect her privacy, so Britain's newspapers seized Wednesday on what appeared to be a rare slip of the tongue suggesting that her unborn baby is a girl.
The Duchess of Cambridge, 31, was overheard telling a well-wisher offering a gift for the new royal heir that she would take it "for my d...", before stopping herself, according to media reports.
Sandra Cook, 67, said the exchange took place during Kate's visit to the northeastern English port of Grimsby on Tuesday, when her five-month-old pregnancy bump was clearly visible.
"The lady next to me gave her (Kate) a teddy bear and I distinctly heard her say: 'Thank you, I will take that for my d...'. Then she stopped herself," Cook said.
"I said to her: 'You were going to say daughter, weren't you?' She said: 'No, we don't know.' I said: 'Oh, I think you do', to which she said: 'We're not telling'."
The exchange made the front page of most of Britain's newspapers on Wednesday, amid growing excitement about the new royal baby.
"Has Kate given the game away?" asked the Times, while the Daily Mirror more confidently declared: "It's a girl!"
The baby will be third in line to the throne, behind William and his father Prince Charles.
William, who married Kate in April 2011, is expected to reveal later this month whether he will continue with his job as a military search-and-rescue helicopter pilot or devote himself more fully to royal duties.