The thorn is displayed behind a crystal window and is identified by a Latin inscription: 'Ista est una spinea corone / Domine nostri ihesu cristi' ('This is a thorn from the crown of Our Lord Jesus Christ').
The reliquary is a wonderful example of the art of émail en ronde bosse. Pearls and rubies are arranged alternately around the compartment which holds the relic. Two sapphires are incorporated into the design: one at the apex and the other used as a mount for the thorn itself.
A dramatic scene of the Last Judgement surrounds the relic, featuring the Virgin Mary (to the left), St John the Baptist (to the right) and Christ (centre). Around the outside are arranged figures of the twelve Apostles with God the Father at the top. At the bottom, four angels sound trumpets as the dead emerge from their tombs.
Behind the figure of God is a gold relief of the Holy Face on the cloth of St Veronica, a fragment of which may have been held in the secondary compartment at the reverse. This is protected by two gold doors decorated with reliefs of Saints Christopher and Michael. The doors are delicately stippled, suggesting that they too were once enamelled. A sensational story supports this suggestion.
When the reliquary came to the British Museum in 1898, its full history was unknown. However, it had been on loan from the Geistliche Schatzkammer, Vienna to the 1860 Exhibition. After the exhibition it was sent with four other items to the workshop of Salomon Weininger for restoration. Weininger made fakes of each item to take the place of the originals, which he sold. Only in 1959, when the fake reliquary was brought to London and compared with the original, was the truth established. The fake reliquary has enamelled doors on the reverse - a detail which a forger would not invent - indicating that the original enamel must have been lost or removed between 1860 and 1898, when it came to the British Museum.
Who was the original owner of this outstanding object? Research has indicated that the two enamelled plaques on the front of the castellated base relate to Jean, duc de Berry (1340-1416). An inventory dating from 1401-3 describing the possessions of the Duc de Berry mentions a grand, imperial crown set with four Holy Thorns which was broken up and its components re-used.