THE father of a former Hong Kong male model who was executed by the Khmer Rouge along with his girlfriend in 1994 has received a message from British Prime Minister Tony Blair. Mr Blair told David Chappell that his son was not forgotten and he would try to bring those responsible to justice. Mr Chappell received the letter this month after he wrote to Mr Blair to ask whether Khmer Rouge commander Sem Bo, who ordered his son's killing, and three other murderers, had yet been arrested. The Lamma Island-based former RAF navigator said he wanted them brought to justice after another leader who executed Westerners was arrested. Mr Chappell feared the guerillas could be living freely or had joined the Royal Cambodian Army. Dominic Chappell, 25, Australian Kellie Wilkinson, 24, both former Hong Kong residents and part-time models, and their friend Tina Dominy, 23, were kidnapped in April 1994 by guerillas and shot dead the next day. They had been travelling on the notorious Highway 4 from their restaurant in Sihanoukville to buy supplies in Phnom Penh. The senior commander, Nuon Paet, who ordered the killings of another three Westerners kidnapped from a train in Kampot three months later, has been arrested and is expected to face trial next month. Mr Chappell said in his letter to Mr Blair, written on April 12 - the fifth anniversary of his son's death - that former Khmer Rouge guerillas were being reintegrated into Cambodian society following their surrender. 'This being so, four of the murderers of my son and his companions are presumably living freely despite being convicted killers,' he wrote. Mr Blair responded: 'The anniversary of your son's tragic death must be a particularly painful time for you and your family. 'I can assure you that we have not forgotten your son or the other British citizens murdered by the Khmer Rouge. We have made clear to the Cambodian Government at every opportunity that we expect them to bring those responsible to justice.' The Khmer Rouge defections should make it easier for authorities to arrest those responsible, Mr Blair said. British diplomats had been able to obtain information from defectors about the killing of bomb-disposal expert Christopher Howes, and Nuon Paet would face trial soon, he said. 'I appreciate that these steps, however encouraging, cannot diminish the distress of knowing that all but one of the convicted murderers of your son and his companions are still at large,' Mr Blair wrote. He had ordered British Ambassador George Edgar to 'renew his messages to the Cambodian authorities that we expect them to apprehend these people'. Mr Edgar had asked they question Ta Mok, known as 'The Butcher', about the kidnap and murder of British citizens. Mr Chappell attended the 1995 trial of Chuon Mean, a foot soldier sentenced to 15 years' jail for taking part in the execution of Dominic Chappell and his companions. Dominic and Kellie Wilkinson were reportedly well known around the Lan Kwai Fong nightclub scene.