Darren Hickey, Rudolf Petschi, Peter Kennedy and Stanley Shaw had gone to Chechnya to install equipment for a new mobile phone network. The deal had been brokered between Surrey-based Granger Telecom, for whom three of the men worked, and the state-owned Chechen Telecom. Mr Kennedy was contracted by British Telecom.
The men were under the protection of Chechen Telecom who were providing security for them at their house in the north of the capital, Grozny. While the men were aware of Chechnya's reputation as a lawless place where kidnapping was common, they had no idea their presence would anger some in the government.
But it seems this is exactly what happened. Inquiries in Moscow suggest the men were kidnapped on the orders of senior government officials who secretly controlled an alternative telecommunications network.
Lechi Alisultanov, an official with Chechen Telecom, made the revelations during a detailed interview with the Independent on Sunday in a Moscow cafe. The quietly spoken, dapper man appeared nervous as he gave his account, constantly checking other tables for eavesdroppers.
He made no request for money, and none was offered. He had been contacted by this newspaper after it learned through a third party that he was anxious to describe what had occurred.
Mr Alisultanov, 36, said the telecom engineers were seized on the orders of senior Chechen government officials who covertly control a rival mobile phone contract. Granger's system was expected to be popular in Chechnya: unlike the existing mobile connection, via a company called Moskovskaya Sotovaya, Granger's phones would not have been routed through Moscow. That meant they were less likely to be monitored by the Russian security services.
He said the abduction happened at 3.20am on 3 October last year when the men were asleep in their one-storey redbrick house. A gang of 11 masked men leapt over the fence, shot the men's mongrel dog, and escaped with their hostages before their three bodyguards - who were in an outhouse - could intervene.
Until then, Mr Alisultanov's relationship with the Western engineers had been close. He says that every day he escorted them on the three-mile journey from their digs to their workplace. In the evenings, they would drop into his house to watch football, and at weekends they went together on trips up the winding roads into the nearby Caucasus mountains.
"I am responsible for the security of my guests. If something happens to them, it is a disgrace and insult to me and all my relatives," he said.
Mr Alisultanov claims that the kidnappings were carried out by a gang controlled by Arbi Barayev, a young man who has become the most notorious player in the Chechen kidnapping business. The men were taken to the Urus Martan area, a rural region 20 miles south of Grozny which has become the stamping ground of Barayev and his bandits. At one stage, the same group also held the British aid workers Jon James and Camilla Carr, who were held for 14 months before their release last September.
Although Barayev is an advocate of fundamentalist Wahhabi Islam, his chief interest was cash. "Barayev's only concern was to get money," said Mr Alisultanov. They wanted $2.5m (pounds 1.6m) a head. "We said we simply don't have that kind of money," he said.
At this stage the issue became complicated by the Chechen teip - or clan system. Mr Alisultanov was from a teip which had long been in conflict with Barayev's; so even more determined to act, he and his associates kidnapped one of Barayev's henchmen - an aide called Apti Abitayev. All negotiations with Barayev instantly stopped. Five days later, the severed heads of the four men were found in a sack on a road 25 miles from Grozny.
Appalled by the murders - which he concedes may have been triggered by the abduction of the rebel Abitayev - Mr Alisultanov agreed to hand over their hostage to the authorities. They expected Abitayev to be prosecuted for kidnapping. Mr Alisultanov says that, to his surprise, Abitayev was released under the orders of the deputy prosecutor-general as part of an agreement for the return by Barayev of the men's bodies to Britain.
"The rules simply don't function in Chechnya," he said. "We are people, not dogs. So we mean one day to punish everyone involved."
These revelations are in contrast to the findings of the Metropolitan Police officers who travelled to the region to investigate the deaths for the coroner.
Their report concludes that "it is not possible to establish with any degree of accuracy exactly why the four engineers were murdered".
It adds: "It is perhaps most likely ... that the engineers were the unfortunate victims of warring mercenary factions."
Granger Telecom has declined to comment on the case before the conclusion of the inquest into the men's deaths. However, it is understood that the victim's relatives are unhappy that the police have been unable to establish anything conclusive.
Last night a spokesman for Mr Hickey's family said they were concerned by the latest revelations. "At this stage we cannot comment on them but would ask that the information be passed to the coroner," he said.