For millions of believers, it is the most precious and powerful of all the Christian relics.
Kept under lock and key inside Turin Cathedral, the mysterious Holy Shroud has inspired generations of pilgrims and provoked bitter controversy.
But according to an astonishing new theory, the features imprinted on the Shroud of Turin are not those of Jesus - but belong to Leonardo da Vinci.
The medieval painter, scientist, biologist and sculptor has long been suspected of faking the image of Christ.
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Now, a study of the facial features suggests the image is actually Leonardo's face, imprinted on the cloth using primitive photographic technology.
The discovery was made by Lillian Schwartz, a graphic consultant at the School of Visual Arts in New York.
Using computer scans she found that the faces on the Turin Shroud and Leonardo da Vinci share the same dimensions.
Schwartz came to prominence in the 1980s when she made detailed measurements of the Mona Lisa and a Leonardo self-portrait and scanned them into a computer.
To her amazement, the two faces lined up perfectly, suggesting he used the self-portrait as a model.
Earlier this year she used the same technique to compare another Leonardo self-portrait with the Turin Shroud.
'It matched. I'm excited about this,' she said.
'There is no doubt in my mind that the proportions that Leonardo wrote about were used in creating this Shroud's face.'
According to a Channel Five documentary due to be shown tomorrow, Leonardo da Vinci created a sculpture of his own head and scorched his facial features onto the linen using a primitive photographic device called a 'camera obscura'.
He hung the fabric over a frame in a blacked-out room and coated it with a substance to make it light-sensitive, like photographic film.
When the sun's ultra-violet rays passed through a crystal lens in one of the walls, Leonardo's three dimensional model was projected on to the material, creating a permanent image.
Shroud researcher and author Lynn Picknett said: 'It is spooky, it is jaw-dropping, and it is, I think, the most exciting thing that has ever happened.
'The faker of the shroud had to be a heretic, someone with no fear of faking Jesus's holy redemptive blood.
'He had to have a grasp of anatomy and he had to have at his fingertips a technology which would completely fool everyone until the 20th century.'
The programme says Leonardo had no problems faking Christ's burial cloth. It also claims he was the only person in that era with the talents and knowledge to produce it.
He was not only fascinated with optical equipment and lenses - his notebooks contain one of the earliest drawings and descriptions of a camera obscura - but he dissected bodies at a hospital morgue.
As such he would have known how anatomy worked and had access to corpses and blood for the shroud.
Mrs Picknett added: 'If Leonardo could have known that 500 years after he died generations of pilgrims are still crossing themselves over the image, I think he would have laughed quite a lot and felt that he had succeeded in what he set out to do.
'He had a hunger to leave something for the future, to make his mark for the future, not just for the sake of art or science but for his ego.'
Although the Turin Shroud remains a popular attraction for tourists and pilgrims, most people now concede it is a fake.
Radiocarbon dating in 1988 showed that it was probably made between 1260 and 1390. There is a 99.9 per cent certainty that it was made after 1000 AD.
If the dates are correct, the shroud was made more than 60 years before the artist's birth in 1452.
However, supporters of the Leonardo theory say his forgery could have been commissioned to replace an earlier version that was exposed as a poor fake which had been bought by the powerful Savoy family in 1453 only to disappear for 50 years.
When it returned to public view, it was hailed as a genuine relic, and experts say it was actually Leonardo's convincing replica.
Some believers refused to be swayed by the arguments. They say the scientists studied a patch of shroud that was replaced in Middle Ages when the original was damaged.
Click to view image: 'fd376ad09c62-3.jpg' According to the Channel Five documentary, da Vinci created a sculpture of his own head and 'scorched' his facial features onto the linen using a primitive photographic device called a 'camera obscura'
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