A convicted kidnapper who held the principal of the German School in Thessaloniki hostage three years ago, returned to the institution during a furlough yesterday armed with guns and explosives but was talked into giving himself up within three hours. Costas Arabatzis surrendered after holding three school officials hostage and demanding 10 million euros as he threatened to set off five kilos of explosives. Police said Arabatzis, 55, was also armed with three hand grenades and two handguns when he entered the school shortly before noon. The job of police negotiators was made substantially easier because, unknown to Arabatzis, a school secretary had noticed the hostage situation developing and immediately went to each classroom to inform teachers who put into action a fire evacuation plan. Some 500 pupils aged 7 to 18 had been safely moved to an adjoining plot of land and police had arrived on the scene before Arabatzis realized what had happened. The kidnapper was left holding hostage the principal, Rolf-Victor Siedenhans, administrator Xenophon Altidis and a teacher. «At times he was calm and said he didn’t want to harm us, but then he would threaten to press the detonator,» said Siedenhans. Police talked Arabatzis into letting all three hostages go. Soon afterward he gave himself up as well. The experience will have been eerily familiar for Altidis as he was one of two people that Arabatzis took hostage during a raid on the school in May 2006, which also ended without bloodshed. As was the case three years ago, Arabatzis had demanded money to pay off debts in Germany. The 55-year-old had been convicted of kidnapping twice before his 2006 raid on the German School, which he also conducted while on furlough.