Betting in Britain is set to heat up as soon as the Duchess of Cambridge goes into labour.

The Royal baby is now thought to be four days overdue.

Rory Scott is with Irish bookmaker Paddy Power.

He says this morning that an event like this is worth millions in Britain.

"Once Kate goes into the hospital, based on 2013 we'd expect to do probably $50-60,000 a day. So it's pretty serious cash."

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British punters appear almost certain the royal baby will be a girl called Alice.

Rory Scott says most people are thinking pink.

"70% of the money is for a girl, or on a girls name, which in a two horse race when apparently they don't even know seems crazy to me."

Alice is the front running girls name, set to pay out 6 to 4.

People can bet on anything from the name and sex of the baby, to what colour dress Kate will be wearing once she leaves the hospital.