A SECURITY guard who killed two colleagues during an armoured van holdup to protect his identity was yesterday sentenced to death by the High Court. The mandatory penalty was handed down by Mr Justice Ryan on Chiao Wing-kin, 24, after a jury found him guilty of the murders of Mr Kwan Chi-man, 31, and Mr Chow Kam-ming, 20. The judge also sentenced Chiao, whom he said was the organiser of the raid and the recruiter of the others involved, to 12 years' jail for robbery. If the Governor decided to commute the death penalty to a jail term, the two sentences would run concurrently, he said. The judge also sentenced three other men, Lau Fai-wing, 22, Lau Kwai-sun, 22, and Ko Wing-cheong, 21, to nine, eight and 10 years' jail, respectively, for the manslaughter of Mr Kwan and Mr Chow and for the robbery. The jury trying the four men, who had all admitted the robbery charge at the beginning of the trial, found Chiao guilty of the capital offence but the other three guilty of the lesser offence. The judge also sentenced a fifth man, Cheng Ming-wah, 35, who had earlier pleaded guilty to a charge of assisting an offender, to 18 months' jail. Senior Assistant Crown Prosecutor Mr Arthur Luk called evidence that the two guards, both covered in blood, were found near an armoured van parked on an unnamed road in Tai Wai on August 8, 1991. Their necks were slashed and they had been stabbed in the chest. A total of $1,257,476 in cash and 527 cheques collected by the guards were taken by the robbers. The court was told Chiao was let into the van because he was wearing his Securicor uniform. Mr Luk yesterday told the court that Cheng was arrested two days after the incident. Under caution, he admitted he lent his Ma On Shan home to the gang to use as a ''staging post'' to change clothes and to split the proceeds of the robbery. He was promised $50,000. Mr Peter Callaghan, for Chiao, said that in view of the mandatory sentence for murder, the penalty imposed on his client for robbery would be academic and he had nothing more to say in mitigation. Counsel for Lau Fai-wing, Lau Kwai-kin and Ko, Mr Paul Loughran, Mr Kenneth Chan and Mr Stephen Franklin, respectively, all pointed out that their clients had offered to plead guilty to manslaughter at the outset. M r Loughran said his client was responsible only for hiring the car used in the holdup and Mr Kenneth Chan said Lau Kwai-kin acted only as driver while Mr Franklin said Ko had profited little from the robbery. Cheng's counsel, Mr Guy Holland, said when Cheng agreed to lend his flat to the gang, he did not expect the consequences.