'This is Darko. I think I know the location of $20million worth of stolen art - I hope you have WhatsApp.' It's a line that wouldn't sound out of place in a heist movie. But that was the anonymous call that helped art sleuth Christopher Marinello, 53, track down nine paintings including works by Chagall and Rivera stolen from an LA mansion. 'I got this tip-off from a shadowy figure in Slovenia called Darko,' said the London-based founder of Art Recovery International. Scroll down for video . Art detective Christopher Marinello has tracked down £250million worth of stolen art including this 1920 Henri Matisse painting Le Jardin . 'He sent me images of the paintings via WhatsApp and we set up a sting operation with the LAPD and recovered nine of paintings which were stolen in broad daylight six years ago.' The art detective is no stranger to high profile cases – having been central to the recovery of a £1billion Nazi-looted hoard found in a squalid Munich flat in 2012. He currently represents the heirs of renowned art dealer Paul Rosenberg in their bid to recover Henri Matisse's 1921 Femme Assise. It was discovered amongst other priceless works in a flat owned by Cornelius Gurlitt, the son of Nazi art dealer Hildebrand, and has been valued at around £60million. He is representing the heirs of art dealer Paul Rosenberg in their bid to recover Henri Matisse's 1921 Femme Assise (left) which was found in a squalid Munich apartment along with this Marc Chagall painting (right) 'The painting was found covered by a layer of grime. There was a milky white film on it as it had been sitting flat, unstretched amongst rotting food,' said Mr Marinello. 'It didn't even have a frame, but there is no doubt that it is the original Matisse. It has been tested by a number of experts and the Rosenberg family has an incredibly detailed archive. 'It should clean up nicely and we were able to determine it has not been directly touched since Matisse completed it.' The reclusive eccentric died in May last year and left the collection dubbed the 'greatest find of the post-war era' to Kunstmuseum Bern. The museum announced that it would accept the immense trove of art amassed by a Nazi-era art dealer, but would ensure any looted art was returned to the rightful owners. And just yesterday it emerged that Germany has signed an agreement to return Matisse's Femme Assise to the Rosenberg heirs. In the past two decades, Mr Marinello has tracked down £250million worth of stolen art including priceless works by Picasso, Renoir and Matisse. The founder of Art Recovery International examines evidence relating to Matisse's Le Jardin with head curator Lars Bystrom . He tracked down nine paintings including Les Paysans by Marc Chagall (pictured) stolen from an LA mansion . One of his most recent cases saw him recover El Greco's 1944 'Portrait of a Gentleman', which was seized from Julius Priester's collection by the Gestapo in Vienna. Mr Priester, a prominent art collector, had fled to Paris with his wife Camilla six years before, when Austria was annexed into Germany as part of the Anschluss in 1938. Last month Mr Marinello also tracked down two sculptures which were stolen with weeks of each other from Hirschl and Adler Gallery in New York 32 years ago. Paul Manship's 'Central Figure of Day' was taken during an exhibition in December 1983 and just three weeks later 'Figure of Gertrude Vanderbilt Whitney' by Prince Paul Troubetzkoy disappeared from the same show. Another of his most high-profile successes was the recovery of Matisse's Le Jardin after it was stolen from the Museum of Modern Art in Stockholm by a burglar armed with a sledgehammer. More than 1,400 artworks were found in a squalid Munich flat owned by Cornelius Gurlitt, the son of Nazi art dealer Hildebrand . Criminals are both nemeses and friends to the detective and if you spot him sitting in a Starbucks, the chances are he's about to sit down with an art thief. 'I've met with a criminal who's been holding onto some very valuable artwork for over 30 years several times at a cafe in Paris,' said Mr Marinello. 'I often receive and exchange stolen works in pubs and cafes. In fact if you see me sitting alone in a Starbucks, there is a high likelihood I'm not just having a cup of coffee. I prefer meeting in public places, as it can get interesting. 'I deal with criminals if I have the permission of the authorities. If the theft happened 25 years ago, the police aren't as interested and in those cases I'm given permission to handle the case myself.' Before he became the public face of the company, he used to work undercover and once set up a sting operation to catch a man trying to illegally obtain a Van Gogh picture worth £2million. He has also recovered a multi-million pound Devo painting from the middle of the street in Manhattan from a celebrity who unwittingly came into possession of the stolen artwork. 'I was meeting a well-known celebrity at the corner of a street in New York and suddenly a beige Mercedes Benz pulled up and the window rolled down. Out came a Devo painting rolled up in a tube inside a black plastic bag. 'That is definitely one of the more unusual places I have exchanged artwork.' Finding the missing art in the first place is a major undertaking as Mr Marinello and his team often locate stolen works before law enforcement. To do this, they have developed Art Claim, the world's most technologically advanced database for stolen, looted and missing works of art, antiquity and cultural property. Once a missing artwork is entered into the database, they use image recognition software to scour catalogues at Sotheby's, Bonham's, eBay and other auction sites until they find a match. 'It all starts with Art Claim. Anyone who has a theft whether it's a museum or holocaust victim should report the theft, then we search art fairs, online sellers, and auction catalogues. 'There is a huge risk in buying a stolen work as the legal fees can be back breaking. The publicity alone can be hugely damaging to a high net-worth collector. 'People spend hundreds of thousands and do absolutely nothing to check the provenance. You need to know in advance what you're buying.' Mr Marinello believes art theft is on the rise and said it is now the third highest-grossing criminal trade, behind guns and drugs. Cornelius Gurlitt's father Hildebrand (right), was commissioned to obtain artworks on behalf of Adolf Hitler (left) and bought works confiscated from Jewish families . 'It is worse than ever. The economic downturn over the past few years, security cuts at museums and wars have all contributed to the fact that cultural property theft is on the rise.' But Hollywood-style art heists with James Bond-style equipment and elaborate getaways are not the only way that priceless works disappear. 'Art is stolen in every way imaginable, but it is not always a well thought-out endeavor. 'Some thieves just see a work and think 'I can just put this in my bag and get out of here'. 'What they don't realise is that these works are not at all easy to sell on. Once an artwork is on our database - as this one is - we will be searching art markets all over the world for it. 'Art can also be lost in transport and there is also insider theft. Of course there are also movie-style elaborate break-ins. Methods are getting creative, but we are trying to stay one step ahead.' 'Thieves are always going to be thieves. Art thieves are common thugs. There's no romance there. The same people who'd steal your wallet would steal artwork. 'The Internet has made it easier track but it's easier for the criminals as well.'
Christopher Marinello has tracked down £250million worth of stolen art .
He was central to recovery of £1billion Nazi-looted hoard found in attic .
Detective set up sting to return nine artworks stolen from LA mansion .
Art theft is third highest-grossing criminal trade, behind guns and drugs .