This week the British Museum announced that it is to display the Holy Facecloth of Christ in the summer as part of an exhibition of Christian relics. Jesus is said to have wiped his face with the towel, imprinting his likeness and giving it the power to cure leprosy.
Attempting to explain the cloth's special aura, the museum's curator said: "In the Middle Ages it would have been greeted in the same way David Beckham's sweaty shirt would be greeted today. It is an ordinary object made extraordinary by the person claimed to have come into contact with it."
Relics have been long associated with pilgrimage, and Ireland has a long association with both. To the medieval Christian, getting up close and personal to a holy object was like getting close to God.
Pilgrims travelling to holy places would purchase relics to bring home to their village, believing they were physically bringing a piece of holiness into their community.
But when Henry VIII broke with Rome and sacked the monasteries, countless Irish relics were burned or spirited away to the Continent for safe keeping. The hand of St Brigid is said to have made its way to Portugal shortly after Henry's clampdown.
More recently, the traffic flow has reversed. In 1836 what are said to be the remains of St Valentine were donated to the Carmelite Church on Dublin's Whitefriar Street, where they attract large crowds each Valentine's Day. In recent times several saintly relics have toured Ireland, but in terms of crowd pullers none has matched St Therese of Lisieux, whose remains drew thousands in 2001 and 2009.
The Prior of Whitefriar St, Fr David Weakliam, is a former science teacher with an open mind. He believes that relics remain relevant and valuable as instruments of worship in the 21st Century. "It's all to do with prayer," he says. "People like the tactile, the sense of being close to something holy. Some people will pray, venerate or meditate more intensely in the presence of a relic."
We don't yet know whether the relics of any Irish saints will be showcased in the British Museum's Treasures Of Heaven exhibition. Items confirmed include three spikes said to be from the Crown Of Thorns, fragments of the True Cross, the foot of St Blaise and the breast milk of the Virgin Mary.
Many picked for display will be relics ranked as First Class by the Vatican. Class One relics are items directly associated with Christ, such as the thorns or the splinters of the Cross, or the body-parts of a saint. Even among First Class relics, there is a pecking order. The head of a notable holy thinker might rank above his feet, while the relics of martyrs are prized above those of saints who died peacefully in their beds.
Class Two relics include items of clothing worn by a saint, or possessions such as prayerbooks or rosary beads. Class Three relics possess holiness by association, and many are pieces of cloth which have been rubbed against first or second-class artifacts.
The British Museum will have taken every care to check that the relics on display are the genuine article, but for the curators and for the multitudes expected to visit, it must all boil down ultimately to good faith.
Holy relics have earned a bad reputation down the centuries, often with good reason. Following the Reformation, the Protestant churches banned and burned them as devices for extracting money from the gullible. One of the chief grounds for this purge was the miraculous, some would say highly suspicious, tendency for relics to clone themselves over and over.
At the last count, upwards of a dozen churches have claimed possession of the severed head of John the Baptist, while three other shrines claim to have one of his hands.
Just this week Canadian film-maker Simcha Jacobovici claimed that his latest documentary will make "a compelling case" that two iron nails unearthed in Jerusalem were used to fix Jesus to the cross. He can join a long queue. At least 30 nails from the True Cross are currently venerated at various shrines.
As they inspect the fragments of the Cross in the British Museum this summer, sceptics will remember the words of religious reformer, John Calvin, who remarked centuries ago that you could build a large ship from all the splinters of the cross on display across Europe.
Fr Weakliam has considered all the arguments for and against, and believes it is down to the individual to decide what's probably authentic and what's probably not. He says that some artifacts being touted as genuine are so preposterous as to bring the whole area into disrepute.
In the case of St Therese, he says: "She only died in 1897 so we can be reasonably certain that her relics are authentic."
While acknowledging that there may be genuine remains of St Valentine in other shrines, he says that there's every reason to believe the ones held in a casket in Whitefriar St Church are authentic.
He explains: "We know that the grave of Valentine was marked by the early Church, and that the remains gifted by Pope Gregory XVI in 1836 were taken from that grave."
But despite every precaution available, the gap in the market for fakery remains. One brazen fraudster even attempted to flog lockets containing air breathed by Jesus.
It goes with the territory. Most Christians would be amused or appalled (or both) to hear that an item called The Holy Foreskin Of Christ has changed hands for money, but it has, many times.
Supposedly, the Holy Foreskin was saved by an old woman after Jesus's circumcision and disappeared for 800 years, until an angel presented it to the Emperor Charlemagne. Within a few hundred years 18 European towns claimed to have the one true foreskin, leading to unseemly squabbles between rival parishes.
Fashions change in devotion just as in everything else, and the western Catholic Church has effectively scrubbed the January 1 Feast Of The Circumcision from its calendar.
The last known Holy Foreskin was stolen from an Italian village in 1983.