In Rome’s basilica of Santa Croce in Gerusalemme, there is a small fragment of wood behind a grille. On it, in faded letters in three languages - Hebrew, Greek and Latin - you can just make out the words: Jesus of Nazareth, King of the Jews.
This, according to the tradition of the Church, is the Titulus Crucis, the inscription that Pontius Pilate ordered nailed to the top of Christ's cross on Good Friday. The Gospel of John records that it was written in all three languages so that everyone passing could read it.
The story of how it came to Rome begins with Helena, mother of the Emperor Constantine. When her son legalised Christianity in 313 AD and set about transforming the empire's relationship with the new faith, Helena, then in her seventies, made a pilgrimage to Jerusalem. There she oversaw excavations that uncovered the tomb of Christ, the True Cross, the nails of the Crucifixion, and the Titulus itself.
She sent the relics back to Rome, where she kept them in her imperial palace on the Caelian Hill. That palace eventually became a church - the Basilica di Santa Croce in Gerusalemme, whose name reflects the earth from Calvary that Helena allegedly spread beneath its floor.
The Titulus was rediscovered inside a wall of the church in 1492, in a lead box. It has been there, more or less, ever since.
Whether or not you accept the relic's authenticity, standing beneath it in the days after Easter, in a church built by the woman who changed the fate of a religion, is an extraordinary experience.