It is the biggest legal fight the art world has ever witnessed: a Russian oligarch, who claims he was ripped off buying multi-million-dollar masterpieces, versus a Swiss art dealer who says it was just business.

Now, after six years of lawsuits in multiple jurisdictions, the tables appear to be turning once more in a saga so dramatic it's been given a name worthy of a movie script: "The Bouvier Affair."

Russian fertilizer tycoon Dmitry Rybolovlev has pursued Swiss art dealer and freeport storage magnate Yves Bouvier around the world for years in various courts, claiming to have been swindled out of $1 billion on 38 exorbitantly priced artworks sold to him by Bouvier over the course of a decade.

But in a new twist, Bouvier has told CNN he is preparing his own billion-dollar damage countersuit against Rybolovlev, after taking legal action in Singapore in February, alleging a long-running court battle with Rybolovlev has ruined his businesses and reputation.

The cases so far have kept an army of lawyers and reputation managers employed on either side, as one allegation against another is levied by each party, including claims of intimidation and political intrigue.

Fittingly, the tortuous imbroglio also involves some of the most priceless and controversial pieces of art, including the 2013 purchase of what is now the world's most expensive and enigmatic painting: the "Salvator Mundi," thought by some to be the work of Leonardo da Vinci despite years of debate over its authenticity -- a work on which Bouvier made a markup of more than 50%.

Long believed by others to be a copy or the work of Leonardo's studio, the "Salvator Mundi" was purchased in 2005 by a consortium of speculative art dealers for under $10,000. Eight years later, after the painting had been restored and declared the work of the Renaissance master, Bouvier bought it for $80 million after enlisting the help of a poker player to beat down the price.

The dealer swiftly sold it on for $127.5 million to his then-client, Rybolovlev, via the pair's offshore vehicles, according to an invoice referred to in court papers, and taking a 1% commission. And while the oligarch later auctioned off the painting for an astonishing $450 million in 2017, to a secret buyer now widely believed to be Saudi Arabia's Crown Prince Mohammed bin Salman, he nonetheless alleges that Bouvier defrauded him -- a claim Bouvier denies.

Rybolovlev declined to be interviewed for this story, but a spokesperson for Dmitry Rybolovlev's family entities told CNN: "These matters are being fought in the courts where we expect to prove what happened and that Bouvier's fanciful story is false. For now, what is most notable is what Bouvier does not dispute: as an art adviser, he pretended to help his clients assemble an art collection at a cost of $2 billion while secretly reaping half of that price for himself."

Yet Bouvier does dispute he was ever an "art adviser," a matter that has at been at the heart of the litigation and allegations by Rybolovlev of breach of trust."

I am an art dealer," he told CNN. "The contracts prepared by Rybolovlev's lawyers and all my invoices explicitly described me as 'the seller.'

"Rybolovlev has never managed to convince a single judge or prosecutor otherwise, in any jurisdiction, for the very simple reason that his allegations do not match the reality of our contractual relations."The saga of the legal battle encompasses many of the problems regulators have identified with the soaring global art market -- art, in the wrong hands, has become yet another commodity to move money with little accountability.

The "Salvator Mundi," meanwhile, hasn't been seen since the record-breaking sale. But it has been back in the headlines after a French documentary claimed in April that the painting had been at the center of a diplomatic spat between Paris and Riyadh, amid doubts over its authenticity and a request by the kingdom that it be shown in the Louvre.

CNN reached out to the Kingdom of Saudi Arabia for comment but is yet to receive a response.

In the documentary, "The Savior for Sale," an anonymous high-ranking French official claims that Prince bin Salman was adamant that the "Salvator Mundi" be displayed next to the "Mona Lisa" in order to solidify its place as an authentic Leonardo -- despite ongoing questions about whether the work is entirely by the Italian master.

The French government ultimately decided not to exhibit the painting under the Saudis' conditions, which the anonymous official says in the film "would be akin to laundering a piece that cost $450 million." Even with the painting out of the public eye, art historians and experts have continued to debate whether the "Salvator Mundi" is an autograph Leonardo or whether he merely contributed to a painting that was predominantly executed by his workshop. The difference could affect its value by hundreds of millions of dollars, given that there are fewer than 20 authenticated Leonardo paintings in the world.

A true Leonardo?

It seems that even those seeking to profit from the painting had doubts about its authenticity.

Emails shared with CNN by Bouvier appear to show communication between Bouvier and a representative of Rybolovlev in which the dealer advised his client in 2013 that the work was a thing of beauty but not a good investment. It was so heavily restored, the dealer wrote, that experts doubted the work was entirely completed by Leonardo himself, and neither the Vatican nor any major world museum had expressed interest in acquiring it.

"The hands are the best-preserved bits," reads Bouvier's email, dated March 22, 2013, while "the rest of it has largely been restored."In another email, Bouvier writes that any "buyer who acquires this painting that no one wants at too high a price will be seen as a 'pigeon' and become the laughing stock of the market and will lose credibility," given the "very low original proportion that appears to have been painted by the hand of Leonardo himself."

Bouvier nonetheless arranged to borrow the "Salvator Mundi" (with a $63 million deposit, he said) from Sotheby's. He claims he then arranged for it to be delivered to the Russian's penthouse in Manhattan in a "black document holder."Antoine Vitkine, the filmmaker who spent two years producing the recent documentary, told CNN he was taken aback to learn that Bouvier, who began his career as an art world outsider, was among those to cast doubt on the painting's credentials given that more prominent experts have authenticated the "Salvator Mundi."

"That's extraordinary," Vitkine said, adding that he thinks some prominent art historians who have risked their reputation on the "Salvator Mundi" were more lax than they would normally be when it comes to weighing in on a rediscovered painting.

Among those to throw their weight behind the attribution to Leonardo was the UK's National Gallery, which exhibited the "Salvator Mundi" in 2011 and catapulted it into the global spotlight. The painting's unveiling was, at the time, widely covered by the press, including CNN."You have to remember, so many people have a stake in this work," Vitkine said.

A bitter back and forth

Bouvier has always denied the charges of fraud leveled against him by Rybolovlev, who has seen his own share of tabloid controversy, including a headline-grabbing divorce and the purchase of an eye-wateringly expensive property from Donald Trump years before the former president took office.

The Russian oligarch, who is president and co-owner of AS Monaco Football Club, is fighting charges in relation to a bribery scandal of Monegasque officials in connection with the Bouvier litigation, in a case dubbed "Monacogate" by the French-language press.

Lawyers for Rybolovlev said in a statement "As far as these allegations are concerned, Dmitriy Rybolovlev remains presumed innocent. He is completely confident about the outcome of this case, in which, after more than three and a half years of investigation, no convincing evidence against him could be found."

In the last six years, Bouvier has fended off legal action in Monaco, Singapore and Hong Kong. A $380 million suit, launched by Rybolovlev against Sotheby's for allegedly helping Bouvier inflate his prices is still ongoing in New York. That litigation sprang back into the public domain on May 7, when Rybolovlev's legal team amended their complaint for the first time in two years to include the sale of a Henri de Toulouse-Lautrec painting on behalf of Rybolovlev by Sotheby's via Bouvier, claiming it was hard to recoup the price paid on the work because of its inflated value. Rybolovlev also claimed in the amended complaint he was not paid the $9.5 million the auction house owed him over the sale. Sotheby's is contesting the claim.

The onslaught of litigation has, according to Bouvier, turned his life upside down. "I used to be an entrepreneur, someone with many businesses and a family firm built up over 50 years," he told CNN."Since all this started, all I've done is spent my time defending myself in court and my reputation in the press," said Bouvier, who admits he made $40 million by flipping the "Salvator Mundi" in two days.

Text messages presented in the French documentary -- not independently confirmed by CNN -- appear to show Bouvier claiming to Rybolovlev's aides that he couldn't secure him a better price than the amount the Russian eventually paid."That's a very good deal for my company. I'm not going to complain," said Bouvier when asked about the large difference."You have to understand what this was like," said Bouvier. "I was blacklisted by the auction houses, the banks wouldn't extend credit (to me, and) I had to start selling off assets to keep my staff and my businesses."

Bouvier claims he has been spied upon and followed by various individuals he does not know. Via a representative of his own he shared with CNN an 81-page private investigation he appears to have shared with prosecutors in Geneva, codenamed "Buldog" which he had commissioned from a Swiss security firm named 4CTM. Beyond concluding he had been tailed by a group of men the firm believed to be British as part of a "very big budget operation," the report was not able to further identify the people allegedly tailing Bouvier. Asked by CNN about the alleged surveillance, Rybolovlev's representative had no comment.CNN reached out to 4CTM security for comment on their report but is yet to receive a response.

Exploiting the art world's opacity

To author and filmmaker Ben Lewis, whose 2019 book "The Last Leonardo" details the drama surrounding the "Salvator Mundi," the public fight between Bouvier and Rybolovlev lifts the veil on the art market's ugly side."

The Bouvier Affair is a classic example of what can go wrong in the secretive, opaque, and -- in inverted commas -- discreet art market," said Lewis during an interview with CNN in London, who notes that parts of the art world have developed a rocky reputation for its way of doing business.

"Opacity, lack of transparency, greed, tax evasion, money laundering, art historical dishonesty, dissembling, disingenuousness, corruption. I mean, where does it end?"But the secrecy, hefty markups, and legal contention involved in the "Salvator Mundi" scandal are not representative of the vast majority of art transactions, says art collector and expert Kenny Schachter."

The fact that people always say the art world is so unregulated and has a dark side is a bit of an exaggeration," said Schachter, in a phone interview with CNN, adding that art isn't any more corrupt than other industries involving multi-million-dollar deals, such as real estate, jewelry, and banking. "No matter what it is, when there is a lot of money, there is going to be bad actions.

"But when it comes to secrecy that does exist in certain facets of the art world, Bouvier is not only a conduit for valuable artworks -- he has built a career on helping the rich keep valuable works hidden from view. As well as having been a major investor in the Geneva freeport, a huge, high-security storage facility where collectors and galleries hold artworks in tax-efficient warehouses, the Swiss dealer has helped establish new freeports in Luxembourg and Singapore.

Bouvier told CNN that Russia also expressed interest in having its own tax-exempt Freeport.

In 2016, a year into his legal woes, Bouvier said he was approached by Yury Trutnev, Russia's deputy prime minister and a personal friend of Rybolovlev, with a proposal to help build one in Vladivostok, at the behest of President Vladimir Putin. A photograph, shared with CNN by Bouvier, appears to show Bouvier and Trutnev meeting in Singapore. The Swiss dealer also shared various emails, which CNN was unable to independently verify, seemingly showing Russian officials inviting him to join the project.

The Russian freeport ultimately never went ahead. But Bouvier claims that he asked Russia's deputy prime minister to intervene in his dispute with Rybolovlev in return for his help on the project."I did mention (to Trutnev), 'I have some legal issues with one of your fellow citizens,'" Bouvier said. "He told me, 'I'll take care of it.' That was when I understood: The message was 'If you help me sort this problem out, I'll make yours go away.'"CNN reached out to the Russian government and Trutnev's office for comment but is yet to receive a response."I might do business with Russia in the future -- why not? It's a country of great culture but I'd never do business with an oligarch again," Bouvier said.

Russia's Kremlin-connected elite is already under scrutiny over its art holdings: A report published by the US Senate's Permanent Subcommittee on Investigations in 2020 claimed companies linked to two other Russian oligarchs with close ties to the Kremlin had exploited the art world's opacity to evade sanctions.

The findings prompted Senators to call for greater transparency in the fine art sector."It is shocking that US banking regulations don't currently apply to multimillion-dollar art transactions, and we cannot let that continue," Ohio Senator Rob Portman, the committee's chairman, said in a statement at the time.

Art masterpieces often pack high dollar value into a small, portable canvas, Lewis says. "Fifty million bucks in a suitcase, right? And who's to say how much it's really worth?"

The European Union and UK have also bolstered regulations on art sales with anti-money laundering legislation adopted in 2020. Those regulations require auction houses and art dealers to do due diligence on new customers for any transaction that exceeds about $12,000.

"There's been a steady increase in compliance regulations," Schachter said. "It's a big misperception for people to think that the art world is just this cesspool... maybe it was more like that in the past, but there's definitely been a clamping down."

Schachter also notes that storing art in freeports is relatively common and usually done for legitimate reasons, such as not having enough wall space for a vast art collection.

"A real collector is someone who is not really hindered by the lack of space to hang something or the lack of money to buy something because collectors just have to have it and they'll always figure out a way -- sometimes illicitly, but mostly not," he said. "I don't think everyone in the art world are angels, but I don't think that (freeports) are purpose-built for evasion or money laundering."

Still MIA

Against the backdrop of legal wrangling, there is one question on the lips of everyone in the art world: Where is the "Salvator Mundi"?Bouvier doubts recent reports that it's on Prince bin Salman's yacht, as was alleged in 2019.

"To put a painting like this on a yacht, with the sea air and the evaporation would be utterly stupid. I cannot believe the buyer would put this painting in a setting like that," Bouvier said."It is on a wood board, which can warp in no time," he said, referring to the walnut panel on which the artwork was painted.

Vitkine speculates that "it might be that we see it one day in the Louvre Abu Dhabi. Who knows?"

Meanwhile, Lewis thinks it could be in a palace in Saudi Arabia, ready to be unveiled -- perhaps before the end of this year -- as part of the kingdom's drive to brand itself as a hub for arts and culture. "The important thing about the art market is that behind the most beautiful objects often lie the ugliest of motives," he said. "'Salvator Mundi' means 'Savior of the world.' And in a way, the painting is now not so much Savior of the world, as the Savior of Saudi Arabia."

Meanwhile, with the legal wrangling between the painting's former owners resurfacing once more, this valuable masterpiece and others once in the same collection, continue to test many a reputation.