A gang of expert burglars at an historic Sussex country house escaped with a haul of antiques described as "unique, irreplaceable and priceless."

The crooks knew exactly what they were looking for amid the treasures of Uppark House, near Chichester.

The late 17th Century stately home boasts an extensive collection of antique paintings, furniture and ceramics.

The thieves managed to evade the home's security measures at 12.30am on Monday, although an alarm did wake staff.

Despite their quick response, the burglars escaped with seven precious items.

Among them was a pair of Napoleonic Sevres Ormolu vases made at the height of the French Empire.

Diana Owen, National Trust Sussex area manager, said: "Any loss from the collection is very upsetting for the staff and the family who donated them.

"We hope to be able to recover them as they are so unusual that it makes them easily identifiable."

The Mead-Fetherstone Haugh family donated the items to the trust in 1954.

Most of them had been rescued from a fire that devastated the house in 1989.

Mrs Owen said: "The items belong to the trust because they are held for the nation.

"They will never be sold and so they have never been assigned a monetary value - for us, they are priceless."

While detectives appeal for information, staff at Uppark hope antique dealers will raise the alarm if someone tries to sell them anything from the haul.

Mrs Owen said: "We have extensive security at all our properties but we will review the security at Uppark as a result of this burglary."

Detective Constable Alan Pack said: "The burglary appears to have been well planned but we won't be disclosing how the offenders entered the property.

"If anyone has any information on the burglary or where the stolen items are, they should contact Chichester CID on 0845 6070999."

The stolen items include a mantle clock described as empire bronze Dore with painted bronze and griotte marble and a pair of Napoleonic Sevres Ormolu vases.

They have panels featuring Danae and the Venus of Urbino and reverse panels with fruit ledges on blue Royale grounds.

The necks have garlands of flowers on gold grounds.

A tortoiseshell Boulle box and an ormolu and tortoise-shell inkstand and inkwell were also taken.

Uppark was built in about 1690 in a fashionable domestic style derived from the Netherlands - a simple brick house with prominent stone dressings and a high pitched roof.

The Fetherstone Haugh family bought the house in 1747 from the descendants of the First Earl of Tankerville, who built the house.

It stayed in their family until the 1930s when it was passed to the Mead family.

Uppark House manager Sarah Stevens said: "Sir Matthew and Lady Sarah Fetherstone Haugh came from Northumberland and had inherited a large sum of money from an uncle. Sir Matthew bought Uppark and a baronetcy.

"Their son Harry did not have children. It was passed on to the Meads family, before the Second World War, as long as they took on the name."

People touring the Georgian interior in South Harting are not allowed to wear sharp heels or ridged soles to avoid damaging the delicate floors.

The servants' quarters in the basement are shown as they were in Victorian days, when HG Wells' mother was housekeeper.

The Meads took expert care of the property and Admiral Mead and his eldest son Richard decided to donate the house and its contents to the trust 50 years ago.

Workmen fixing lead work on Uppark's roof in 1989 started a fire which destroyed the private rooms on the upper floors.

Luckily, it was an open day and visitors helped to save most of the huge collection of antiques on the ground floor.

The trust spent the next five years restoring the building.