Treasures of Heaven, British Museum, London

As I looked round this new exhibition at the British Museum, two unrelated incidents, one from the secular and the other from the religious world, came to my mind. A Texas gold trader last week paid more than £1m for a leather jacket worn by Michael Jackson in the video for “Thriller”; and, four years ago, 160,000 people were reported to have applied within a few days to receive a free handout of snippets from a vestment worn by Pope John Paul II. In both cases, we are dealing with something that is both fundamental and ancient in our culture: the notion of the relic, first as something of high value and, second, as an item of mass popularity.

Treasures of Heaven has turned the space under the dome of the old Reading Room at the British Museum into an ecclesiastical space, gleaming with the gold and silver of liturgical objects and echoing with 12th-century choral polyphony. The purpose is to explore what relics meant to our medieval ancestors and to see how they were valued and collected, housed and enhanced, prayed to and fought over.

They are all Christian relics, either of Christ himself (the most highly valued) or, more often, of the saints. The latter were the superstars of the medieval world, the only names universally known across Christianity, just as likely to be invoked on an Armenian mountainside as on an Irish offshore rock. Saints were regarded as being proactive in the human world, changing luck, effecting cures, finding lost things and missing people and even, on occasion, reversing death.

But the saints were no longer here, in person, to work their miracles. This awkward fact was circumvented by giving these powers to their relics. A shred of shrivelled flesh, a bit of grey bone, might look uninspiring but, contained in their reliquaries – a carved rock-crystal flask, set in a jewelled surround of gilt silver facings and enamel pictures, or intricately carved ivory figures – they became objects of mystery, and of desire.

Popes, emperors, kings and doges outbid each other to get them. In 1204, Constantinople was disastrously sacked by a crusader army to a large extent because of its vast quantity of reliquary treasure – and, whenever serious relics were acquired, the best artists were commissioned to embellish them or to beautify further their existing embellishments. Louis IX of France built the magnificent Sainte Chapelle in Paris to keep his collection, and no great cathedral worth its name lacked its quota of relics contained in magnificent reliquaries.

As this exhibition shows, some of the most astonishing craftsmanship you are likely to see was brought to bear. Well over 100 of these caskets, monstrances, hollow crosses, miniature buildings, sculptures and structures, such as arm reliquaries, that took the shape of the relic in question, have been gathered together by the British Museum – many from its own collection but others borrowed, and not only from Europe. Some very old reliquaries of St Menas have come from Egypt, while the architectural, jewelled 13th-century Shrine of St Amandus is from Baltimore. Exquisite Limoges enamelling, micro-mosaic work and ivory carving is used to enrich objects that are very often, in themselves, beautifully designed and proportioned, especially those made during the cultural explosion known as the 12th-century Renaissance, a high point in reliquary production.

The vibrant, extravagant economy of relics did not exist only for the aggrandisement of kings but also for the encouragement of popular devotion. It was usual on saints’ days for the arm bone or shrivelled finger of the saint to be publicly paraded in its golden, bejewelled and illustrated reliquary. At the same time, centring on the network of medieval pilgrimage sites, there was a thriving peripheral trade in actual or (much more often) faked relics. They took the form of tiny fragments of bone, hair and scraps of clothing that could be worn around the neck in a decorated locket or entombed in the heart of a private altar. Cities such as Cologne, where the alleged remains of the Three Kings were kept, Santiago de Compostela (St James the Apostle) and Canterbury (the martyred St Thomas) were medieval huckster heaven.

The display of objects in this show makes them, in all but a few cases, highly legible, and enhances their beauty. Meanwhile, the whole presents an opportunity to think about the material superstructure of Christianity and the enormous efforts it once put into translating its spiritual values into tradeable physical objects. It is something that, in this post-Christian age, we are still doing.

‘Treasures of Heaven: Saints, Relics and Devotion in Medieval Europe’, until October 9,

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