'Henry' has turned out to be the most popular royal baby name for people placing bets in Norfolk.

Ladbrokes is offering odds on the name and gender of the royal baby, whose arrival is being eagerly anticipated now that the Duchess of Cambridge has gone into labour.

The biggest bet staked in Norfolk at Ladbrokes to is £50 at 20/1 odds on the baby being called Henry, with the average stake being around £5.

The odds for Henry were previously stacked at 50/1, but due to the popularity of the name they have fallen to 20/1.

Alex Donahue, from Ladbrokes, called the popularity of royal baby bets 'incredible', but said the average stake was low compared to sports bets.

He said an average Norwich City game could bring in £1.5 million of bets, while the royal baby will probably only see around £1 million in the industry nationally.

He attributed this to the popularity of royal baby bets with non-regular betters having a small flutter, as opposed to seasoned betters who tend to place higher stakes. Meanwhile nationally Coral said it is taking bets on not only the name and gender of the baby, but also the date of arrival, weight, and hair colour.

The biggest bet Coral has had nationally is a £5,000 4:5 bet on the baby being the girl, with the lucky punter set to win £9,000.

'The amount of bets dwarfs anything we've seen before,' said a spokesperson for the company. 'It's the busiest royal baby ever in betting terms.'

Nicola McGeady, spokeswoman for the firm, said: 'The whole world has been waiting for Kate to go into labour and now that she has, we have witnessed another betting frenzy.

'Punters have been anxiously clutching onto their betting slips for months now and if the money talks, the baby will be called Alexandra, with brown hair, weighing 7lb to 7lb 15oz, an outcome which will prove a nightmare result for the bookies.'

Paddy Power said some £30,000 was taken in bets in the three hours following the announcement that Kate was in labour.

Bets on the birth date have been suspended. Odds on the name Isabel/Isabella were cut from 25/1 to 10/1 following large bets placed on the prospect it could be William and Kate's chosen name for a girl.

Paddy Power even opened bets on the colour of Pippa Middleton's dress if she visits the baby in hospital.

William Hill said it hoped the arrival was not a girl because of how well backed it was in their royal baby markets - when bets were suspended on the sex, the odds stood at 8/15 for a girl and 11/8 for a boy.

The favourites at William Hill for a girl's name are Alexandra (7/4), Charlotte (6/1) and Diana (12/1), while the most popular boy's names are George (8/1) and James (10/1).

William Hill spokesman Joe Crilly said: 'Royal baby betting has been incredibly popular and it looks like we may finally be able to pay out on the markets. We are excited that the birth is imminent, we just hope the young one is not a girl named Alexandra.'