The Fatimid rock crystal vessel with mounts by Jean-Valentin Morel. At the sale at Chrsitie’s on October 7, it is estimated to realise in excess of £3m.

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Fatimid rulers conquered Egypt in 969 and renamed their new capital city Al-Qahira (The Triumphant), which remains the Arabic name for Cairo. Ewers were amongst the works of art made in varied media to reflect this name through their cultural opulence.

Such lavishness could not be maintained indefinitely and by the mid 11th century the state had become so impoverished that much of the Royal Treasury had to be sold, explaining the sudden dispersal of these ewers; in a "fire sale" which was recorded by a Fatimid Treasury official in Kitab al-Dhakhai'ir w'al-Tuhaf (The Book of Gifts and Rarities.

Carved from a single piece of flawless rock crystal, which is as hard as toughened steel, the ewers were hollowed out and then decorated by hand with extraordinary finesse, leaving a surface in the thinner areas that is only a couple of millimetres thick.

Almost all surviving examples have come through cathedral treasuries and each is decorated with animal groups associated with hunting, surrounded by arabesque designs.

Of the other six examples, one is in the Victoria & Albert Museum, London, having been bought privately in 1862 (decorated with a hawk attacking a deer); two are in the treasury of the Basilica of San Marco, Venice (one decorated with a lion, the other a ram); one is in the Cathedral of Fermo, Italy (decorated with a falcon); another is in the Louvre, having been in the treasury of the royal Abbey of Saint Denis, Paris (decorated with a small falcon), and one well-documented ewer (decorated with falcons) was stolen from the museum in Limoges in 1980 and not yet recovered.

In 1998 another example in the Pitti Palace, Florence (decorated with partridges), was apparently broken beyond repair.