DSK's ex-wife Anne Sinclair claims Nazis took Matisse painting from her grandfather The painting is one of many belonging to the late Parisian art dealer Paul Rosenberg that the Nazis stole His descendents have been trying to retrieve them for decades A lawyer representing his granddaughter Anne Sinclair has put in a formal claim to Sitting Woman, found in the Munich flat of Cornelius Gurlitt A lawyer representing the ex-wife of Dominique Strauss Kahn is making a formal claim on Sitting Woman, a previously unknown painting by Henri Matisse found amid a trove of more than 1,400 artworks in the Munich flat of an elderly recluse. The painting is thought to be worth up to £60million and is one of many belonging to the late Parisian art dealer Paul Rosenberg that the Nazis stole and that his descendants have sought for decades to retrieve. Chris Marinello, the director of Art Recovery International, is acting for Rosenberg's granddaughter Anne Sinclair, who was the third wife of the disgraced former IMF chief. Remarkable: A painting from Henry Matisse called Sitzende Frau (Sitting Woman) - one of the previously unknown works found at Gurlitt's flat - is projected on a screen during a news conference in Augsburg. Anne Sinclair is laying claim to it In a phone call to MailOnline Mr Marinello revealed that he met with the Rosenberg family on Thursday and has drafted a letter for the German authorities claiming ownership of the Matisse. He said: 'We're hoping that they will accept our offer of a meeting in Munich.' The painting, he explained, was confiscated from Paul Rosenberg's gallery in Paris. He then fled to New York and upon his return to Paris after the Second World War could not find the artwork. He was Matisse's art dealer and so received the Sitting Woman directly from the artist himself, Mr Marinello added. It was on display in Paris, but it's not likely that many members of the public ever set eyes on it. Meanwhile, phones in the cramped London offices of the Art Loss Register have been ringing off the hook since German prosecutors announced what the register's chairman, Julian Radcliffe, calls "the biggest cache of illegally stored art since the end of the war." "People who are registered with us have been ringing to say, `You're on the case, aren't you?"' Radcliffe said Wednesday. Relationship: Anne Sinclair (right) divorced Dominique Strauss-Kahn (left) the former director of the IMF, in March 2013 The flurry of activity follows the discovery in Germany of more than 1,400 artworks - some by modern masters such as Marc Chagall, Henri Matisse and Pablo Picasso - stacked in the Munich apartment of an elderly man. For families whose treasures were stolen by Germany's Nazi regime, the discovery has raised hopes - but also stirred frustration. Citing an ongoing tax probe into the apartment's resident, German authorities have not revealed many details about the vast majority of the paintings, drawings, engravings, woodcuts and prints they have found. At a news conference Tuesday, officials described only a fraction of the spectacular find, including - tantalizingly - previously unknown paintings by Matisse, Chagall and German artist Otto Dix. That has sparked a clamor for information from art hunters, museums and the lawyers of those seeking to recover looted art. Holding place: Cornelius Gurlitt, lived off the collection and as a consequence he has managed to survive his entire life without any official bank account, pension or insurance. Pictured: The Munich apartment where officials discovered the hidden paintings A reproduction of a painting by Italian painter Canaletto presented during the news conference on Tuesday that could be worth £10million Treasure trove: An allegorical scene painting by Marc Chagall worth an estimated £15million had never been seen by the art world before emerging from Gurlitt's collection The Munich trove was found in early 2012 at the home of a man whom German officials didn't name but who has been identified in media reports as 80-year-old Cornelius Gurlitt. His father, Hildebrand Gurlitt, was an art dealer who acted for the Nazis in the 1930s to sell art considered "degenerate" by the regime - including Impressionist and modern masterpieces - outside of Germany in return for cash. Some of the works were seized from museums, while others were stolen or bought for a pittance from Jewish collectors who were forced to sell. Gerhard Finckh, director of the Von der Heydt-Museum in Wuppertal, western Germany, called for an inventory of the Gurlitt trove to be published online quickly so museums can find out whether their stolen works are among them. Collector: Hildebrandt Gurlitt amassed more than 1,500 masterpieces and ordered them to be destroyed in 1945 "If our works are among the discovered art, we will do everything to get them back," said Finckh, whose museum lost pieces by Dix, Paul Klee, Vassily Kandinsky and many others. Jewish groups also have called for the works to be made public immediately. Spokesman Steffen Seibert said Wednesday that Chancellor Angela Merkel's government favored releasing information about works that "may have been confiscated from people persecuted by the Nazis." But he gave no details or timeframe for that to happen. That leaves people seeking the return of artworks with no quick path to restitution. Imke Gielen, a Berlin lawyer specializing in restitution claims, said prospective claimants should approach the Bavarian prosecutors with queries about specific works. She said it was vital to prove ownership of the artwork until Jan. 30, 1933, the day the Nazis seized power. Any art lost after that is presumed to have been sold under pressure or seized, boosting the chances of restitution. Others will turn to the Art Loss Register, which maintains a database of several hundred thousand works of stolen or missing art. The organization's team of art sleuths, historians and legal experts was busy on Wednesday trying to match works on its database with the items found in Germany. Radcliffe says it has already found one match - not the Matisse - but won't say what artwork it is. Although there has been criticism of the Germans' delay in announcing the find, art law expert Coco Soodek was sympathetic. She said the trove is so large that it takes time to catalog the works - and "it might take a decade" to reunite them with their owners. German officials say they have done preliminary work on only 500 pieces so far. "It's like a giant game of `Concentration,"' said Soodek, head of the art law team at Bryan Cave LLP. They will designate the ones that we know to exist and match those up with documentation of stolen art. Those are the easy ones. You match up the ones you can get to first, and then you start a big detective search.