A murder suspect told a court he slit the throat of an old friend in self-defence following a row over a plot to chop another acquaintance. Lam Ting-kam, 20, said he and Wong Chi-fung, 22, were close friends from the moment they met in 1992. But their relationship began to sour on June 11 last year, when Wong embraced Lam's girlfriend at a karaoke bar. In a rage, Lam beat his friend until he lay motionless on the pavement. The next day Wong went to Lam's Yuen Long house to apologise, the High Court heard, but Lam ordered his friend out after an argument. The following day Wong dropped by the flat, Lam said, claiming a row broke out when he overheard Wong speaking on his mobile telephone, arranging for a mutual friend to be chopped. Suddenly, Wong hit Lam on the head with 'a hard object' before scooping up a cutter and chasing him. Lam said he grabbed his own cutter and turned, slitting his attacker's throat. He said he contemplated calling for help, but Wong came up behind him while he was looking at the telephone. 'I slashed his face with the cutter.' His friend hurled a hammer at Lam's head, knocking him out, the court was told. When Lam came to moments later, the hammer was lying beside him and Wong was gripping his legs. 'I picked up the hammer and struck him on the head continuously,' Lam said. Wong's rotting corpse was discovered eight days later in a bag on the roof of the building. A trail of blood led police downstairs to Lam's door. Lam was arrested when he returned to the flat 12 hours later. He has pleaded not guilty to murder. The trial continues before Mr Justice Michael Stuart-Moore.