Salvator Mundi broke the record for most expensive painting of all time when a Saudi prince purchased it for $450 million at auction in 2017. The piece, a portrait of Christ, was presented by Christie's as an authentic work of Leonardo da Vinci, but from the time of the purchase, art experts have been skeptical of that claim. Now, The Guardian reports that an art historian at Oxford University may have figured out who the true artist is: Leonardo's assistant.

In a forthcoming update of his book, titled Leonardo da Vinci, Matthew Landrus makes the case that the majority of Salvator Mundi was actually painted by Bernardino Luini. Luini worked with Leonardo in his studio and was heavily influenced by his mentor's art style. According to Landrus, the gold bands in Salvator Mundi, the fabric of the robes, and the modeling of Christ's face all bear strong similarities to elements found in other known Luini works.

The most expensive Luini painting sold at auction to date cost only $654,545, which would make Salvator Mundi worth significantly less than its selling price if the theory holds true. But Landrus says calling it a Leonardo da Vinci painting isn't completely inaccurate: While Luini painted most of the work, he says that Leonardo likely painted 5 to 20 percent.

Before the painting hit the auction block, scientists analyzed its composition to reveal it contained rare and expensive pigments that would have only been available to an artist of Leonardo's stature in 1500. If the painting did come from Leonardo's studio, but not from his hand, that would explain the inconsistencies many art scholars have pointed out.

Salvator Mundi will be displayed at the Louvre Abu Dhabi this September before moving to the Louvre in Paris next year.

[h/t The Guardian]