Police said just six people demonstrated against the Vienna State Opera Ball last night (Thurs).Officials in the capital put dozens of anti-riot officers on alert to deter possible demonstrators. Up to 2,000 protesters collided with the police at previous occasions of the pompous event which is regarded as one of the cultural highlights of the year by many Austrians.Vienna police announced today that there were no violent incidents around the event last night as they counted just half a dozen of demonstrators voicing their disagreement with the ball.Yesterdays Opera Ball was attended by singer and charity activist Bob Geldof, opera star Anna Netrebko, former Christian Social Union in Bavaria (CSU) chief Edmund Stoiber and Austrias political elite.All eyes were on Viennese playboy Richard Lugner and his star guest, call girl Karima El Mahrough. The 18-year-old, better known as Ruby the Heart Stealer, rose to fame in Italy amid claims she had sex with the countrys Prime Minister Silvio Berlusconi.Ruby who received tens of thousands of Euros to attend the event was enjoying herself waltzing until the early hours of the morning. The TV celebrity was described as “adorable and charming” in most reports by Austrian radio stations and newspapers today.Lugner had his personal Ruby Tuesday when he picked the Arabian starlet up in a chartered jet. Ruby, who was accompanied by a bodyguard at all times, signed autographs for fans at his Lugner City shopping centre the next day before attending the Opera Ball with the businessman and his family last night.Lugner revealed yesterdays Opera Ball could have been his last. “I dont know whether I will be able to cope with all the hectic and chaos another time,” the businessman said.Lugner started inviting VIPs to the ball in 1992. Previous guests of the 78-year-old include Raquel Welch, Andie MacDowell and Dita Von Teese.