The year 1171 marks a turning-point in relations between Byzantium and Venice. The Venetians could never forgive the Emperor Manuel for his high-handed action in arresting and imprisoning thousands of their citizens. Nor could they tolerate his deliberate favouritism of their commercial rivals, the Pisans and the Genoese. They felt embittered and betrayed. The attack on the Genoese quarter in Constantinople in 1170 had been the work of local mobsters. It had not been inspired by the Doge and people of Venice; and the emperor had gone too far in punishing all Venetians throughout his empire. By no means all of them were guilty of the crime. Yet many of those who were innocent, who had by their own profitable enterprise been contributing to the wealth of Byzantium, were ruined and bankrupted as a consequence.

The career of one such Venetian entrepreneur in the Levant is exceptionally well documented. He was that Romano Mairano who contrived the escape of some of his countrymen from Constantinople in March 1171. Romano was one of the nouveaux riches of Venice in the middle of the twelfth century. He married well and invested his wife's substantial dowry in his business ventures overseas. From 1153 he was engaged in trade between Venice and the ports of the Byzantine Empire, at Halmyros and Sparta. In 1155 he took a cargo of timber from Venice to Constantinople and set up a business in the capital which he made his headquarters for the next ten years. It was a family concern.