Kate Middleton 'lets slip' the sex of her royal baby

Pregnant Kate Middleton has reportedly revealed the sex of her unborn royal baby.

The Duchess of Cambridge appears to have let slip the suggestion that the baby she is expecting with husband Prince William is a little girl.

Kate, 31, was visiting the Northern fishing post of Grimsby and meeting a crowd of around 2,000 people on an official engagement when she supposedly made the comments.

The Duchess was given a teddy bear by 41-year-old Diana Burton standing in the crowd.

But it was Sandra Cook, 67, who was standing next to Diana who has set rumours flying, saying she heard Kate say: "Thank you, I will take that for my d..." before stopping herself.

[Related: Kate Middleton opts for MaxMara for first 2013 public engagement]

Sandra continued: "I leant over and 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 replied: 'We're not telling'."

It's not the first time meet-and-greets with the Royal couple have caused wagging tongues, Prince William accepted a baby grow a few months before the royal baby announcement was made, immediately starting the baby rumour mill.

Kate is just over halfway through her pregnancy, with the baby expected in July. She appeared happy and relaxed at the event, showing no signs of her earlier severe morning sickness.

But there is, of course, the old wives' tale that suggests women who suffer with morning sickness are more likely to give birth to a baby girl.

[Related: Kate Middleton shows off pregnancy glow at royal engagement]

If this rumour is true, it will mean the changes to succession laws will indeed mean the daughter of Prince William and the Duchess of Cambridge will eventually become Queen.

Kate kept her bump mostly under wraps, just visible in her chocolate-brown Hobbs coat. She was careful after her earlier 'slip' to refer to her baby as 'it' for the remainder of her visit.

One woman in the crowd asked: "Can you feel the baby kicking?", to which the Duchess replied: "Yes. I can feel it kicking."