According to ITV Royal news producer Georgina Brewer, on a walkabout at a fishing heritage center Tuesday in Grimsby, her first engagement, Kate was given a teddy by well-wisher Sandra Cook, 67.

According to Brewer, Kate took the toy and said, “Thank you, I’ll give that to my d...” and stopped herself.

Ms. Cook, sensing a scoop, asked if she meant to say daughter, and Kate, looking flustered, replied, “We’re not telling,” and swiftly moved on.

The story looks set to dominate Wednesday’s news, with early copies of the Mirrorand the Mail both putting it on the front page.

If Kate really is having a girl, it will be historic moment, as the law was changed in the United Kingdom recently to allow a female firstborn to become monarch.

If Kate has inadvertently revealed the sex of her unborn child, she will undoubtedly be deeply upset to have accidentally invaded her own privacy.

Yet Kate has a habit of giving up confidential information when talking to the public. Last year, after refusing to give out the name of her and Prince William’s dog on the grounds it was a private matter, Kate revealed the name, Lupo, to a group of schoolchildren.

Kate also revealed Tuesday that she can feel her unborn baby kicking.

The slip came when she met dozens of well-wishers while on a visit to Grimsby’s National Fishing Heritage Centre, her first of three engagements.

Kate’s spokesfolks refused to comment.