The contest for the Salvator Mundi came down to two bidders, with the increments jumping at one point from US$332 million to US$350 million in one bid, and then, at just short of 18 minutes, from US$370 million to US$400 million. Gasps were heard in the saleroom, which gave way to applause when

Christie’s co-chairman Alex Rotter made the winning bid for a client on the phone.

In the crowd that November evening was Robert Simon, the New York art dealer who picked up the Salvator Mundi, widely thought to be a badly damaged copy, for under US$10,000 at an estate auction in 2005. Around 20 other copies of the work, by students and followers of Leonardo, are known to exist.

In hindsight, Simon’s discovery sounds like something out of a Hollywood movie. In reality, the process involved painstaking research and restoration over a period of six years, all of it kept secret until 2011 when the Salvator Mundi was unveiled to the public as part of a special Leonardo exhibit at the National Gallery in London.

The newly authenticated work – and the only Leonardo painting in private hands – was later sold for US$80 million to Swiss billionaire Yves Bouvier in 2013. Bouvier then immediately sold the painting for US$127.5 million to Russian billionaire Dmitry Rybolovlev, for whom he was acting as an art adviser. (That deal and other spectacular mark-ups charged by Bouvier have resulted in a protracted and unresolved lawsuit between the two men.)

At the November 2017 auction, Simon thought the painting could fetch as much as US$280 million, but the bidding “just kept going”. When I ask what he thought of the final sales price, he laughs. “I thought it was cheap.” Then he pauses and leans back in his office chair, and continues more soberly. “I’m joking, of course. But also, I’m not. Obviously, it’s a huge amount of money, but it’s a Leonardo.”

For art historians and particularly Leonardo da Vinci scholars, the unearthing of a long-lost painting by the Renaissance master is the discovery of a lifetime. “More remarkable than discovering a new planet”, according to Luke Syson, who curated the Leonardo show at the National Gallery in London.

Leonardo da Vinci’s genius was far-reaching, and his place in the history of Western art and science is enormous. But the Salvator Mundi’s enormous price nevertheless incited controversy. Critics called the sale “obscene”. Media headlines ranged from “Has the Art World Gone Mad?” to “450 million reasons why Leonardo da Vinci’s Salvator Mundi isn’t a masterpiece”. Debates about money and art ensued.

According to Simon, the outcry was misdirected. “No one says anything when someone buys an apartment at 432 Park Avenue or a yacht for US$500 million – that sort of goes under the radar. But for some reason, after the sale, this painting became the poster child for income inequality.”

Adding to the irony, Simon says, is that the Salvator Mundi will be exhibited in a public museum. The anonymous buyer was later confirmed to be Saudi prince Bader bin Abdullah bin Mohammed bin Farhan al-Saud , an associate of Crown Prince Mohammed bin Salman, who bought the painting on behalf of Abu Dhabi’s Department of Culture and Tourism. The work is slated to hang inside the new Abu Dhabi Louvre.

But the uproar was particularly confounding to Simon, given the recent explosion of the contemporary art market, where works with arguably less historical or cultural value, by unproven artists, fetch exorbitant sums. Simon rhetorically asks about the latest prices for Jean-Michel Basquiat – a 1982 painting of a skull had sold for US$110.5 million in May 2017. “How many Basquiats are there? Hundreds. Leonardo has just 15 paintings.”

Nonetheless, it is unusual for an old master painting to break price records.

European old masters generated just six per cent of total global auction sales last year (US$594 million), according to a report published by Art Basel and UBS. The modest percentage will no doubt rise after the Leonardo sale, but the whims of wealthy collectors skew toward impressionist and contemporary artists such as Andy Warhol, Damian Hirst and Jeff Koons, whose works collapse the distinction between high and low art – and traditions of connoisseurship in which art dealers like Robert Simon are schooled.

Simon, who received his doctorate in art history from Columbia University, has built a career seeing distinctions that others can’t: differences in brush stroke, qualities of light and shadow, opacity and texture of the paint. At his gallery, he displays a selection of paintings from his current inventory, primarily Italian and Spanish paintings from 1300 to 1800, which he acquires and sells to museums and collectors.

In many cases, Simon can spot rare gems at auctions that are misattributed, misunderstood or even mistreated, capitalising on them later. And this, in sum, is what Simon did in 2005 when he came across a small painting, thought to be a copy of a long-lost Leonard da Vinci, at an estate auction in Louisiana. He recognised something in the painting and bought it along with another gallerist, Alexander Parrish.

Since the turn of the last century, the painting had been catalogued as a copy by Giovanni Antonio Boltraffio, a contemporary of Leonardo who worked in the master’s studio. It had also been damaged and badly overpainted. Simon shows me a black and white photo of the painting taken around 1900. Christ looks ghoulish – almost cartoonish – with eyes that bulge from his face and a strange, scrappy beard. “This is why the painting wasn’t noticed in its modern history,” Simon says. It also explains how the painting was auctioned for just US$60 in 1956.”

But despite being heavily overpainted, rough patches in the wood panel were still visible, and, by examining photos of earlier versions with the same grain patterns, Simon could verify that the painting in his possession was the same composition as the one found in earlier catalogues. He took the painting to long-time friend Diane Modestini, a painting conservator who teaches at New York University, and she agreed to clean it.

By removing layers of dirt and paint, Modestini exposed the extent of the damage – a large crack in the wood panel and several areas where the pigment was missing – but also revealed the quality of the original painting.

In a photo of the painting post-cleaning, the surface appears luminous. “There are losses here and there where it was glued back together rather crudely,” Simon says, pointing to a damaged portion. “But even though there’s a crack, the human eye can virtually put together the missing parts.”

At this point, Simon says, he still wasn’t sure the painting was the original Leonardo, but he knew it related to a lost painting by Leonardo, and so he proceeded with a restoration. The wood panel had to be restructured, a process that took several months. And Modestini began filling in the missing portions so that the art could “live” again. “Where there were losses, she didn’t try to reconstruct it,” Simon explains. “Our feeling was, it was better to leave it so you could see, close up, where the paint was missing.”

At around this time, two and half years into his research, Simon came across the first major clue that this painting was an original. Through the use of infrared and X-ray imaging, which penetrates through the top layers of paint, he discovered that Christ had two thumbs on his right hand: one in a position consistent with the other Salvator Mundi copies and another earlier thumb that the artist had painted over.

“In all of the other [Salvator Mundi paintings] there is just one thumb,” Simon says. “This one is an early idea by the artist. So once we really understood that it was painted over by the artist, it became clear that this must be the first version.”

Other clues in the fingers were revealed. When Simon and Modestini began comparing the quality of the painting to the copies, looking closely at the way the cuticles and nails had been rendered. The sfumato effect of the face – the soft blurred effect achieved in part by manipulating the paint using the heel of the hand – is also typical of many Leonardo works.

Simon sent the painting to a special lab in Massachusetts for pigment analysis, as Leonardo mentioned in his writings that he preferred using walnut oil to linseed oil (the most common base for mixing pigment). It’s a rather obscure reference, Simon says, but by using a tiny sample of pigment, the lab was able to confirm the painting was, in fact, made using walnut oil.

The discovery was thrilling. But Simon now needed to substantiate his findings. A private viewing was arranged at London’s National Gallery, where scholars and art historians convened from Oxford, Milan, the Metropolitan Museum in New York and the National Gallery in Washington.

It was a rather “surreal” evening, Simon recalls, as he watched from the sidelines as the world’s leading Leonardo da Vinci experts viewed the painting. Their response was unanimous: this was an original Leonardo da Vinci, likely commissioned around the year 1500. Martin Kemp, one of the world’s leading Leonardo experts, said that he knew immediately upon first viewing the restored painting that it was the work of Leonardo. “It had that kind of presence that Leonardos have … that uncanny strangeness that the later Leonardo paintings manifest.”

But though the scholars Simon consulted agreed on the painting’s authenticity, others in the art world expressed scepticism.

In a colourful essay for Vulture.com in 2017, for example, New York Magazine art critic Jerry Saltz called the Salvator Mundi “a two-dimensional ersatz dashboard Jesus” and voiced “big doubts” about its authenticity. He called the painting “inert”, “Byzantine” and too unlike other Da Vinci paintings. Saltz also offered a telling disclaimer: “I’m not an art historian or any kind of expert in old masters,” he wrote, “but I’ve looked at art for more than 50 years …”

Simon hadn’t read the piece but laughs upon hearing Saltz’s verdict. “That’s what the internet does,” he says. “Everyone’s opinion is equal.”

Critics have focused on the condition of the painting, which according to Simon simply reveals ignorance about the general state of old master paintings. And some critics, though accepting the authenticity of the work, simply criticised the painting itself. New York Times writer and art critic Jason Farago disparaged the painting as being bland – boring even. “This Jesus, far from saving the world, might struggle to save himself a seat on a crosstown bus.”

The crystal globe in Christ’s left hand has also been a point of contention. Some critics have noted the reflections are those of a transparent bubble – not the refracted, inverted effects of light passing through a crystal sphere. They argue that Leonardo, who studied such things, would have rendered it more precisely.

In an essay, Diane Modestini described seeing the rock crystal orb through a microscope and finding evidence of Leonardo’s hand.

“Originally the illusion must have been magical,” she wrote, particularly the lower right side of the orb, which contains carefully observed inclusions, characteristic of rock crystal, that are “astonishing” under a microscope. “Each has been described by an underpainted middle tone, bracketed by a curlicue of white, and a dark shadow … only Leonardo, with his interest in the natural sciences, would have gone to such obsessive lengths.”

Despite the doubts, each bit of controversy has also brought renewed attention to the Salvator Mundi, and for this Simon is pleased. “It’s been a good talking point for a lot of people,” he says, suggesting that it may also have generated new interest in the old masters.

“Look at that picture over there,” he gestures to a portrait newly identified as the work of 17th-century Spanish painter Jusepe de Ribera. Entitled A Desperate Woman, the painting depicts a woman in a state of anguish, clutching her hair with tears streaked across her face. “I find that to be a passionate, emotionally charged painting. I look at all of this work in terms of what’s behind it. If it’s a Virgin mother and child, it’s about tenderness, or foreboding or conflicting set of emotions … these are complicated paintings.”

Contemporary art’s focus on intellectual or abstract concepts leaves many people confused, he reckons. The Salvator Mundi, on the other hand, has elicited a tremendous response from viewers. “It’s a remarkable painting. I’m not religious, but I find it very spiritual, very moving. And that’s the level that Leonardo works on. It’s more than just a ‘thing’.”

And yet, the Salvator Mundi was included in Christie’s Post-War and Contemporary Art sale, presumably to reach more aggressive buyers, when it was sold in 2017.

(This article is published in the May issue of The Peak magazine, available at selected bookstores)