Thick wooden doors held back the flames saving historic rooms as fire ripped through Allerton Castle, it emerged yesterday.

Around a third of the eighteenth century building near Knaresborough, North Yorkshire, was destroyed in the blaze early on Saturday morning.

The full extent of the damage was being assessed yesterday by the castle's millionaire owner Dr Gerald Rolph.

As well as destroying a number of private apartments and offices, the fire gutted the castle's oak panelled dining room.

Dr Rolph fears the room's detailed carvings on the walls and ceiling - said to be the finest outside the Houses of Parliament - could be lost forever.

"The dining room was one of the real jewels of this house, with absolutely magnificent hand-carved wooden family crests on two walls," said the Florida-based businessman.

"Everything in there is gone, including the stained glass windows.

"We hope we can bring it back to its former magnificence, although sadly I doubt we will be able to recreate the wooden carvings."

However much of the castle, used for weddings and corporate events, remains intact including the Great Hall, which an insurance claims assessor working at the scene yesterday said was saved by its thick wooden doors.

Meanwhile, the cause of the fire is being investigated after it emerged that a retained crew tackled a small blaze at the castle several hours before the flames fully took hold.

The part-time crew from Knaresborough were initially called to a chimney fire just after 11am on Friday night.

The firefighters spent nearly an hour putting out the fire in the hearth and checking the building using thermal imaging equipment.

However, the crew was called back to the castle arriving just after 4am on Saturday after reports of another chimney fire. By this time the roof had caught alight.

Owen Hayward, operations support manager for North Yorkshire Fire and Rescue Service, said: "We need to establish the cause of the main fire.

"From that we will be able to determine whether there's a link between the two incidents."

During the eighteenth century, Allerton Castle was owned by Prince Frederick, the Duke of York, brother to King George IV.