Ever since the middle ages, pieces of the True Cross, and other relics such as saints' bones, have been sold to the gullible. But now the trade in bogus relics has moved online, to the fury of traditional Catholics. They are even more alarmed at the sale of "genuine" relics, which is also picking up pace as monasteries and convents close and their treasures come on the market. In theory selling a relic is an offence under Church law, warranting immediate excommunication. But what is a genuine relic, and how its provenance proved? Jolyon Jenkins goes on a deep dive into a world where faith, science and archaeology collide. Producer/Presenter: Jolyon Jenkins, BBC Audio in Bristol