The future heir to the throne is due two months today.
The Duchess of Cambridge, Kate Middleton, is expected to give birth on July 13, the Mail on Sunday reported last night.
The official due date has been a secret but the newspaper quoted a friend of the royal couple as saying: "Some of Kate and William's closest pals were at a barbecue hosted by a family friend of the royals recently. They were all discussing the fact that Kate's baby is due to be born on July 13.
"Everyone was very excited."
The Mail on Sunday said mystery has shrouded the expected date of birth since the Duchess was rushed into hospital with severe morning sickness in December, early in the pregnancy.
The Palace was forced to announce she was expecting before her 12-week scan, meaning no one outside Kate and William's close circle knew exactly how far the pregnancy had progressed.
The paper reported that the birth due date falls in the middle of the Coronation Festival, a four-day celebration to mark 60 years since the Queen was crowned, 16 months after being proclaimed Monarch on her father's death.
"The baby is expected to be delivered in the private Lindo Wing of St Mary's Hospital in Paddington - where William was born - under the supervision of royal gynaecologists Alan Farthing and Marcus Setchell," the newspaper reported.