Freeman, the author of Holy Bones, Holy Dust: How Relics Shaped the History of Medieval Europe, studied early descriptions and illustrations of the shroud. None predates 1355, the year of its first documented appearance in a chapel in Lirey near Troyes in France, before it was acquired by the House of Savoy in 1453 and “converted into a high-prestige relic” to shore up the power base of the insecure Alpine dukedom.

In particular, he turned up a little-known engraving by Antonio Tempesta, an artist attached to the Savoyard court, who made a meticulously detailed image of one of the ceremonial displays of the cloth to pilgrims in 1613.

“Astonishingly,” he writes, “few researchers appear to have grasped that the shroud looked very different in the 16th and 17th centuries from the object we see today.”

The Tempesta engraving, as well as a number of 15th- and 16th-century first-hand descriptions, emphasise a feature that is much less obvious now – that the figure was covered in blood and scourge marks, relating to Christ’s flagellation. These extensive markings can be explicitly related, argues Freeman, to a focus on blood in depictions of the crucifixion that emerged in the 14th century – a “dramatic” change in iconography that sharply differentiates depictions of the crucified Christ from those of earlier centuries, and which reflects revelations of a bloody, wounded Christ reported by mystics such as Julian of Norwich in the 14th century.

The original purpose of the shroud, argues Freeman, is likely to have been as a prop in a kind of medieval, theatrical ceremony that took place at Easter – the Quem quaeritis? or “whom do you seek?”

“On Easter morning the gospel accounts of the resurrection would be re-enacted with ‘disciples’ acting out a presentation in which they would enter a makeshift tomb and bring out the grave clothes to show that Christ had indeed risen,” he said.

Freeman’s idea was shored up by his study of the earliest illustration of the shroud – on a pilgrim badge of the 1350s found in the Seine in 1855. On it, two clerics hold up the shroud, and beneath is an empty tomb.