They were powerful rulers of perhaps the mightiest empire the world has ever seen, and their portraits oiled the wheels of diplomacy. Six sultans of the Ottoman empire, which spanned more than six centuries and dominated a great swathe of the world, gaze out beneath magnificent, bulbous turbans, a symbol of their wealth and status. An original set of 14 portraits was produced in Venice in 1579, and copies were made later. The only surviving intact set is in Munich, but a set of six goes on display at Christie’s in London this weekend before being sold at auction on 28 October. “They are colourful and lively witnesses to an episode that was the culmination of a century of exchanges between Europe and the Ottomans relating to imperial portraiture,” said Behnaz Atighi Moghaddam, the head of sale in Christie’s Islamic department. The original set was attributed to Veronese, the Venetian court’s most celebrated artist, and these six copies are attributed to one of his close followers, she said. “None of these sultans were ever seen by the Venetian artists. Veronese would have read ambassadorial accounts describing their characteristics and seen engravings or sketches of them. “Most sultans had nicknames. For example, Selim I was known as Selim the Grim, because he was a fierce ruler and killed many of his statesmen. When you look at his portrait, you can sense that anger. Selim II was known as Selim the Drunk, and you can really see that in his puffy eyes and big cheeks. “The textiles are in [Veronese’s] style – they are so rich and luminous, they look almost 3D. And the subjects have life and dynamism, each with his head tilted or slightly looking back over one shoulder.” The headpieces were a “very Ottoman feature”, Moghaddam said. “The more important someone was, the bolder these distinctive turbans would be, sometimes with gold ornaments or jewels.” Gifts were “the oil that greased the wheels of diplomacy in the medieval and early modern eras, and the Ottomans made numerous demands of the Venetians,” she added. The set on display at Christie’s has been traced back to the collection of Count Gustav Adelmann von Adelmannsfelden, who had family connections with the Ottomans. The portraits, which were kept in a Bavarian castle until 1935, are expected to sell for up to £1.2m.