Five years ago its editor, Martin Monestier, was publishing an antiques price guide, with a free page on which readers could report stolen items. The service was so popular that it doubled the guide's circulation. Setting to work on the Yearbook, he discovered an enormous trove of absent artworks. The Yearbook lists 8,000 pieces, each worth more than pounds 5,000, and often much more.
Monestier estimates that art worth pounds 600m has been stolen in Europe over the past five years. The Yearbook devotes 300 pages to paintings, many by old and modern masters, that have vanished from homes and museums, and passed under the apparently untroubled gaze of the dealers and collectors.
But the editor has met a wall of silence from art dealers anxious not to frighten buyers. Details of only seven of the 8,000 missing works came from professionals. One auctioneer accused him of publishing 'a book of rumours'. Three weeks later, the same auctioneer found that he had sold a stolen painting, which was identified in the Yearbook.
While the art world ignored Monestier's Yearbook, details flooded in from European insurance companies concerned about mounting claims, and from police departments such as the French Office for the Suppression of Theft of Works and Objects of Art and the Italian Artistic Patrimony Brigade.
France and Italy, with their immense artistic heritage, offer rich pickings for a new breed of international art thieves. Between 1985 and 1990, the Italian police managed to seize 40,000 pieces from mafia-organised looters of archaeological sites. They admit that four times as many may have slipped over the border, including a 250lb statue of Aphrodite, dating from 450BC, that turned up at the Getty Museum in California.
The cataloguing of such pieces, the first step in preventing their disappearance, will take the Italian Ministry of Cultural Affairs several decades. An inventory begun in 1964 by the French Minister of Culture, Andre Malraux, is still incomplete. It lists 300,000 works of art in 1,200 museums and 680 private collections. Since it was started, 12,000 items have gone missing from the public collections alone.
Mireille Balestrazzi, the divisional commander of the 30- strong French art squad, points out that art thieves can offload their booty with ease, notably in Belgium and Japan. The English are large buyers of French and Italian art, he says, and English thieves specialise in ransom, under the guise of discreet notices promising rewards for recovery. The problem, however, has been to identify works as stolen in the first place. Important works are often altered, the mounts and patinas changed, even details added to disguise well-known oils: Bonnard's Enfant triste acquired a smile. Lesser pieces are simply sent to public auctions.
Monestier believes that the existence of the Yearbook will prevent dealers from being able to use the legal justification that they bought works 'in good faith'. But the specialist thieves are still ahead of the specialist police, catering to what Monestier calls the democratisation of art-collecting since the Sixties. 'In the old days, the networks of dealers and clients were small,' he says. 'Everybody knew who owned what. Now everybody wants to own art, and the supply of art is limited. Once the thieves acted out of opportunity. Now, they plan and select. They've become connoisseurs.'
For example, he says, some of the magnificent collection of Corot paintings stolen from a provincial French museum in 1984 were found in Japan, decorating the home of a gangster boss.