It will not be the news that the journalists and cameramen baking outside the Lindo Wing in London’s longest heatwave in a decade want to hear – Kate’s own mother thinks she may not be due until July 23^rd or 24^th.

For, in a little noticed report published in the Sunday Telegraph earlier this year, at the end of May, the impeccably sourced diarist Richard Eden wrote, as a footnote to a piece about how Kate’s mother Carole had returned a lost dog to its owner, that the future queen mother, “had told friends that the baby will be a Leo. The dates for the star sign, whose characteristics include loyalty and ambition, are July 24 to Aug 23.”

In fact, astrologists are equally divided as to whether the sign of Leo starts on July 23 or July 24.

In all the excitement about the Mail’s now certifiably dud July 13 tip, Eden’s information was overlooked. But, if the baby is born anytime after today, Eden will be closer to the correct date than the Mail.

This morning, the scribe told the Royalist that the tip came “from a friend of Carole’s who told me.”

While Eden is confident in the honesty of his source, he was also taking care not to count his chickens, adding, “To be fair, there are still a few days to go.”

However there are increasing signs that the July 13 date was a flyer from the beginning. Why would William have booked himself in for a weekend of polo on his wife’s due date? Why would her sister have flown to the fashion wedding of the year in Vienna if the baby was due around that time?

Although both the Queen and Camilla have publicly expressed a hope that the baby will arrive soon, there remains the strong possibility that the intensely private William and Kate have not shared the due date even with their employees. For although in off-the-record briefings the palace has said the baby is due in “mid-July” this appears to be simply a repetition of what Kate herself said when asked directly on a walkabout. The only official communication said they were expecting a bbay 'in July'.

Eden’s own child was ten days late, at which point the delivery was induced. A few brief calculations show that if the baby is actually due on July 24, and it comes a week or so late, the press pack could be outside the Lindo Wing until early August waiting for the child to arrive.

“They will have great suntans, won’t they?” Eden said.