Speculation mounts on early arrival of Prince William-Katherine Middleton's royal baby

British bookmakers are taking money on speculation that the royal baby could come sooner than expected with the Duke and Duchess of Cambridge fudging the date to retain some privacy and shake off the world's media.

Prince William and Kate's first child is officially due in mid-July with the couple saying they have no idea of the sex of the baby who will be third in line to the British throne.

But bookmaker Paddy Power on Wednesday cut the odds on the baby arriving in the first week of July to 4-1 from 8-1 after a surge of money from gamblers who believe the couple could be taking a lead from Princess Diana.

In 1982 Princess Diana - who died in a Paris car crash in 1997 - fooled the public by saying William was due on July 1 and he was actually born 10 days earlier.

Bookmaker William Hill said its latest betting activity suggested the baby would be born on July 17 and female. All the bookmakers reported an increase in betting activity on the royal birth as the date approaches.

William Hill said turnover has trebled in the last week with over 50,000 pounds ($77,000) wagered on the various markets and this figures expected to double in the next week or so.

Paddy Power expected royal betting turnover to top 300,000 pounds in coming weeks, a 30 percent increase on the royal wedding in April 2011.

"The imminent arrival has sent a royal bump of joy across the country and it's clear punters love nothing more than a royal flutter," a Paddy Power spokesman said in a statement.

Buckingham Palace sources have said Kate intends to have the baby in the Lindo Wing at St Mary's, in Paddington, west London, where Princess Diana gave birth to both William and his brother Prince Harry. Gamblers are favouring Alexandra, Diana, Charlotte and Elizabeth for girl's names and George for a boy.