Why recovering the Nazi's stolen loot is so complicated

The discovery of a painting missing for 80 years has focused global attention on art stolen in wartime and also explains why only a fraction has been returned

- Guy Walters

It began, absurdly enough, with an estate agent's photograph.

A grainy picture of a living room in a bungalow in Argentina, snapped for a property listing, showed a gilt frame above a sofa. An eagle-eyed researcher recognised the work as Portrait of a Lady, an Italian portrait once in the collection of a Jewish Dutch art dealer called Jacques Goudstikker - a name synonymous with the wholesale dispossession by the Nazis of Jewish collectors in the Netherlands in 1940. Argentinian prosecutors, alerted by the sighting, swept in; the painting was recovered and handed to the courts. The family of the original owner is among those now pressing for restitution. It is a remarkable, if familiar, story: what was taken in wartime surfaces decades later in the most mundane of places.

That fluke also re-focuses a question historians and lawyers have been arguing over for three generations: how much of the art looted by the Nazis is still missing, and what is it worth? The blunt answer is: we don't know - and whatever number you pick, it will be both terrifyingly large and maddeningly imprecise.

Estimates vary. A commonly cited figure is that between 1933 and 1945, some 600,000-650,000 works were seized or sold under duress across Europe. Many were small domestic objects china, silver, family heirlooms - but the haul also included thousands of paintings, prints and sculptures taken from private Jewish collections, museums and synagogues. Only a fraction has been returned.

Put a monetary figure on that and the problem becomes even more slippery.