HOPES of achieving justice for the region's only victim of the killing fields of Cambodia appeared to be fading last night after the investigating judge admitted his inquiry was on the verge of collapse.

The family of 26-year-old John Dewhirst had hoped that a United Nations-led trial of a dozen surviving leaders of the Khmer Rouge would finally reveal details of how he had met his death in the notorious Tuol Sleng interrogation centre, near Phnom Penh.

Months of legal wrangling over courtroom procedures between the 17 Cambodian and 12 international judges have ended in deadlock, and now the senior investigator has said that, unless a breakthrough can be achieved when the next session begins on Monday, then the case will be halted.

Marcel Lemonde, the French investigating judge, said: "If new rules are not adopted, we will not go forward because it would be useless.

"Then we would have to examine the possibility of the international judges asking the UN to withdraw and drop the whole process. It is now or never."

The end of the trial would mean that no one would be held to account for the estimated 1.7m deaths at the hands of the Khmer Rouge.

The most senior figure from the brutal regime to face trial is former maths teacher Kak Kek Ieu - who, as Comrade Duch, was Pol Pot's chief executioner. He ran the interrogation centre and is thought to have ordered at least 12,000 deaths.

Among them was Mr Dewhirst, a Newcastle-born teacher, who was tortured and executed after being forced to sign a ludicrous confession that he was a CIA spy who had been recruited by the Americans while he was a 12-year-old schoolboy at Newcastle's Royal Grammar School.

After spending some time working in Japan, Mr Dewhirst was about to return to his native North-East, but decided on one last adventure holiday before settling down.

With two friends, a Canadian and a New Zealander, he bought a boat to sail to Singapore, but strayed into Cambodian waters where they were intercepted by a Khmer Rouge gunboat.

One of the young adventurers was shot dead, while John and his surviving shipmate were detained. Although he was never seen again, he is believed to have been tortured and murdered days before the regime was finally toppled.