Prince William's pregnant wife has unexpected revealed keenly awaited information about her due date, saying it will be “around mid-July”.

During a two-day tour of Scotland, the Duchess of Cambridge confirmed that her baby is due in mid-July.

"It’s around mid-July but apparently babies have their own agenda,” Kate said as she opened a new outdoor center.

St James’s Palace’s official announcement has previously only said that the baby, which will be a great-grandchild of Queen Elizabeth II, is due in July.

Kate, 31, also said that she and William had drawn up a list of boys’ and girls’ names for their first child - and that she has taken up knitting. "I’ve been trying to knit and I’m really bad. I should be asking for tips," she said.

"We have a shortlist for both (boy and girl) but it’s very difficult. My friends keep texting me names."

And when asked if she had got her nursery ready, she smiled and said: "No... we have got a lot to do!"

British newspapers are abuzz with speculation that Prince William's pregnant wife Catherine is expecting a girl after a member of the public reported hearing what seemed to be a hint that a daughter is on the way.

If the child does turn out to be a girl, she is destined to ascend the throne as queen one day.

Planned changes to the law of succession that end the tradition of a boy taking precedence over an elder sister are already de facto in effect, the British Cabinet Office has said.

The child will be next in line to the British throne after William, whose father Charles is first in line.