It is the first time in recent memory that a dealer discovery has been placed in an exhibition of such standing in this way.
A statement released by the National Gallery reads: "We felt that it would be of great interest to include this painting in the exhibition [opening in London in November] as a new discovery. It will be presented as the work of Leonardo, and this will obviously be an important opportunity to test this new attribution by direct comparison with works universally accepted as Leonardo's."
While the statement maintains that Salvator Mundi, a picture of Christ holding a globe with his right hand raised in blessing, is currently in a private collection in New York, it has been widely reported that that it is owned by a consortium of American dealers being represented by Old Master specialist Robert Simon.
Asked about its ownership status and potential value, Mr Simon told ATG: "It is not on the market so that is not an issue I can discuss. I am not involved in this as a dealer, but it is a project I have agreed to take on."
The picture is believed to have been purchased at an estate auction in the US around six years ago, although the location of the sale, the price paid and the successful buyer have not been revealed. It is thought, however, that it was originally either spotted or bought by another American dealer, Alex Parish.
Mr Simon, who confirmed that Mr Parish "has been involved from the beginning", first saw the 2ft 2in x 18in (66 x 45cm) oil on panel in 2005 and said that he initially thought it was "a fine painting close to Leonardo".
"It was highly compromised by overpaint," he added, "so we weren't seriously thinking it was actually by Leonardo at that stage."
Soon afterwards a comprehensive conservation programme was begun as well as a research project undertaken by Mr Simon into the provenance of the work and its connection to Leonardo.
As the possibility of Leonardo's authorship emerged, the painting was shown to scholars in the autumn of 2007, including Mina Gregori of the University of Florence, Nicholas Penny, director of the National Gallery, and curators at the Metropolitan Museum in New York.
In May 2008, it was taken to London to be directly compared with Leonardo's Virgin of the Rocks in the National Gallery.
There it was studied further by half a dozen other leading Leonardo scholars, including Maria Teresa Fiorio of the Raccolta Vinciana in Milan and Oxford University's Martin Kemp - the scholar who has thrown his weight behind another 'Leonardo' discovery of recent times, the so-called Bella Principessa vellum portrait owned by Paris-based collector Peter Silverman.
According to Mr Simon, the consensus has been "unequivocal" that Salvator Mundi was painted by Leonardo. The only difference of opinion has come with regard to its date.
"Now that it has been restored you can see it has an overwhelming spiritual presence," he said.
Naturally, considerable attention has focused on what this picture could be worth. While the National Gallery's rules prevent any work being exhibited that is for sale, the suggested value has been anything between £100m-200m. Even at the lower end, this would make it the most expensive artwork ever sold.
It will finally go on view at the National Gallery exhibition on November 9 (running until February 1 next year).
By Alex Capon