The £3m Cezanne painting stolen from Oxford's Ashmolean Museum on New Year's Day was not insured against theft, according to gallery chiefs.

A spokesman for Oxford University, which manages the collection, admitted the work, Auvers-sur-Oise, was only covered in the event of fire or flood damage.

"In common with other national and university museums, the Ashmolean does not insure work in its own collections against theft," he said.

Richard Green, curator of the York City Art Gallery, backs up that view. He says smaller art collections balk at the prospect of meeting insurance premiums.

"The reason for not insuring works of art against certain misfortunes is the prohibitive cost."

Many institutions instead put their faith in elaborate security systems, which in the case of the Ashmolean were obviously not enough to dissuade a determined art thief.

In January 1999, Mr Green's collection befell a similar fate, when armed robbers made off with £1m worth of paintings - including a work by Turner.

None of the items were insured against such an event, says Mr Green.

Art galleries are unusual in this respect. Other kinds of museums are mostly able to meet the premiums for their exhibits.

"Fine art does have this high financial value, compared to things like the fossils in the Natural History Museum," explains Mr Green.

It is not only the provincial galleries who go without insurance. A spokeswoman for the Department of Culture, Media and Sport says none of the great national collections are covered.

"The government does not insure its art collections. The premiums would be so enormous it is not feasible," says spokeswoman Ruth Findley.

Mr Green is not surprised the world famous art at the National Gallery is uninsured - even against fire.

"Goodness! The cost of insuring it all would be the same as the gross domestic product of a small country."

However, there are safeguards elsewhere. The government will underwrite works which are housed, but not owned, by a gallery. The Government Indemnity plan is designed to promote the loan of artworks and help stage special exhibitions.

Yet even the return of the Ashmolean's Cezanne, dating from between 1879 and 1882, might not end the museum's trauma.

When thieves broke in under the cover of millennial celebrations, they slashed the work from its frame, making for "just a floppy bit of canvas," says Mr Green.

"If you roll it up it is disastrous. Rolled tightly with the painted surface on the inside it will crack," says Mr Green.

Not only slashed from the frame and potentially damaged in transit, the fragile artwork may also have suffered from being outside the controlled climate of the gallery.

Although theft insurance would never compensate the museum's 250,000 annual visitors robbed of the chance top see the work, it would speed up the restoration process were it recovered.