A 'greedy' teenager who blackmailed his ex-girlfriend for sex and money by threatening to sell erotic tapes of hers was jailed for four years yesterday. Judge Duncan Kilgour told the defendant, a college messenger, it was a 'very, very serious' offence which warranted a jail term. The defendant's behaviour was 'extraordinarily greedy' and 'very unpleasant' because he turned a 21-year-old into a sex slave, the judge said. Defence lawyer Suen Kam-hee told the District Court the defendant, 19, simply did not know how to handle the broken relationship with the victim, who had been with him for nearly two years. Prosecutor Johnny Chan Yue-chow said that when the victim tried to end the relationship, the defendant told her he had secretly made tapes of them having sex. He threatened to make the tapes public and demanded $12,000 in exchange for the non-existent tapes. Between January 27 and February 4 this year, the defendant paged the woman six times and they had sex each time. He was found guilty of 15 charges of procurement of sex by threats, three of blackmail, one of theft and one of committing an act intending to pervert the course of justice.