Throughout this period, the French state-owned company -- which later became synonymous with corruption and scandal -- was allegedly committing human rights abuses against the people of the oil-abundant Niger Delta.

Mr Welby, who made regular visits to the country's capital for meetings at the time, strenuously denies being aware of the claims -- or the true motivation for the Bonny LNG project.

Soldiers paid by Elf seized land from tribesmen in the region, often using violence. And locals say police officers were paid to arrest those who resisted.

During Mr Welby's five years at Elf he worked under a number of colourful characters, none more so than the Corsican-born oil executive Andre Tarallo, dubbed Monsieur Africa.

Tarallo, who was in charge of African operations, would later feature in a massive fraud inquiry that tore the company apart in the Nineties. He was jailed for four years in 2003 for paying millions in bribes to African leaders in return for oil contracts.

'Some of my other colleagues had contact with Tarallo and they were caught with their pants down,' said Mr Welby's former boss, Kjell Skjevesland.

'Justin would have had direct contact with him. Justin would have been in the meetings with him, probably as the only non-French guy in there.' However, Mr Welby denies meeting Tarallo in person.

Elf's headquarters was in Paris near the Champs-Elysees. But, for the Bonny LNG talks, Mr Welby usually travelled to the Nigerian capital Lagos as the company's sole representative. 'He made a meaningful contribution,' said his boss.

Mr Welby, 56, now the spiritual head of more than 80 million Anglicans worldwide, insists that, while he was aware of rumours of corruption during his time at Elf, he never encountered evidence of it.

When he joined the company in the late Seventies, the Nigerian government was planning to nationalise the country's oil fields, something Elf, Shell, BP and others were desperate to prevent.

They attempted to talk the government out of it by dangling a giant carrot -- a promise to invest £6 billion between them in a project that involved shipping natural gas from Nigeria to Europe.

But Bonny LNG collapsed before it began, just as the 'investors' knew it would. 'Everyone was scrambling for crude at the time and everyone wanted to please the Nigerians,' said Mr Skjevesland. 'This project was way, way off and unrealistic.'

He said that the oil companies were simply 'playing games' with the Nigerian government to ensure they could 'still get the crude out'.

Thomas Knutsen was another Elf finance executive who worked with Mr Welby. Asked if the project was designed to trick the Nigerian government into believing it would go ahead, when in all likelihood it would not, Mr Knutsen replied: 'I think that is a good assumption.'

Asked if Mr Welby was aware of the tactic, Mr Skjevesland replied: 'Yes, of course he was.' But the Archbishop insists he 'believed it to be a genuine project .  .  . and nothing [he] learned about it at the time suggested otherwise'.

Unlike the Archbishop, Mr Skjevesland has conceded that he himself was 'probably' aware of the human rights abuses committed by Elf.

After Bonny LNG's demise, the plan to nationalise the industry was halted, ensuring the oil companies' Nigerian interests were saved. They enjoyed massive profits, while the majority of Nigerians continued to lead impoverished lives.

Mr Welby left Paris in 1983 and the Elf Group the following year, but returned to the country 20 years later on numerous Anglican peace missions in the Niger Delta. He risked his life negotiating with Al Qaeda and performed countless acts of courage as he sought a reconciliation between oil giant Shell and the Ogoni people.

It is tempting to see the clergyman's work in the region as a form of atonement for the sins of Elf and the other major oil companies.

These days he rails against huge City bonuses as a member of the parliamentary commission on banking standards. He has written extensively on business ethics, including an academic paper called Can Companies Sin? Few would deny that his five years at Elf left him well-equipped to answer that question.

Tellingly, one of the reasons why Mr Welby left Elf for a much smaller company was so that he was 'better able to both know and influence its culture and practices'.

In the late Seventies and early Eighties, the oil industry (still reeling from the Opec crisis) was at its most morally elastic.

As a member of Elf's financial department, Mr Welby cut quite an uncompromising figure. His boss boasted that his team -- who earned their 'sharks' nickname from a magazine article -- dealt 'on a yes-or-no basis, no short cuts, no maybes, no shaving an eighth of a point'.

Mr Welby, an Old Etonian and a Cambridge graduate, quickly established a reputation as a model employee with a razor-sharp brain.

Mr Knutsen, with whom he shared an office, recalled: 'It was very challenging but we were young and the sky was the limit. I don't think I've been more impressed with a brain than I was with Justin's.'

He was quickly handed responsibility beyond his years. For instance, he was directly involved in an attempted hostile takeover of an American oil company, Kerr-McGee. Hours before it was due to go ahead, the takeover was halted after the intervention of the French prime minister who feared it would damage French-US relations.

Before it was stopped, Mr Skjevesland recalled Mr Welby was instructed by Elf's group treasurer to transfer $2 billion. 'One morning Justin came in to the office and told me, "I got a phone call from New York last night. We're going to go ahead with the acquisition."

'In those days [1980], instead of having huge syndicated bank loans we went to the biggest banks in the world and borrowed say £100 million to £500 million from each.

'For this root money he [the group treasurer] called up Justin. He didn't bother to call anyone more senior because he had confidence in him.' The Archbishop says his role in the deal was exaggerated, but does recall being instructed to draw 'all the maximum funds... on pre-arranged credit lines'.

Home for Mr Welby and his wife Caroline was a duplex apartment on the banks of the Seine in the French capital's smartest district, the 16th arrondissement.

Along with the rest of the finance team, Mr Welby often dined at the temples of Parisien gastronomie. Mr Skjevesland, 67, who now lives in Switzerland, said: 'The banks invited us out all the time.'

But Mr Welby was modest in nature and deed. 'Justin enjoyed dining out but he didn't drink much,' said his boss. 'He wasn't like some of the other Brits. In those days we were floating in alcohol all day long.'

Mr Welby had been a committed Christian since university yet rarely discussed his faith with colleagues. But some recall him wearing a cross pinned to the breast pocket of his tweed jacket.

Isobel Gil-Noble, the warden of St Michael's, the English-speaking Paris church Mr Welby attended, said: 'Justin was a bit of a yuppie -- and a real slick professional.'

Mr Skjevesland, who was the company's assistant treasurer for most of Mr Welby's time with Elf, also attended the monthly talks in Lagos on the Bonny LNG project.

It was at this time, unbeknown to Mr Welby who only learnt of the allegations last year, that abuses were being carried out in Elf's name in the Delta.

Dr Alexander Akor, 55, a lecturer in environmental engineering at the local River State University, said: 'The military was used to suppress the people. They would ask you to leave the area. If you refused, they would intimidate you, beat you up and drag you away. Many families were displaced and people were killed.'

He said Elf had paid the military to remove people from their homes so it could use the land for drilling.

At the time of Mr Welby's visits to Nigeria on behalf of Elf, corruption within the country's government reached its zenith. Its people received precious little of the oil profits, despite revenues accounting for four-fifths of the nation's income.

It is estimated £250 billion has been stolen by corrupt government officials since oil was struck -- leaving 70 per cent of Nigerians currently living on less than 65p per day.

Ibama Ibegwuru, 80, has lived for 40 years in the Egi region where Elf had a major onshore operation. He says he was imprisoned by Nigeria's military junta after protesting against the alleged human rights and environmental abuses committed by the company.

'When the Land Use Act came in [which allowed the military to seize land] nobody could stop Elf,' said Mr Ibegwuru. 'The military used force and some youths were killed; some had their legs broken to intimidate the indigenous people.'

He said the same soldiers taking part in the violent land grabs were also defending Elf's property. In 1993, a settlement was made between Elf and the Egi people. Elf's pledges included employing more local people, settling compensation cases, providing water to the Egi and improving environmental and ecological protection.

Meanwhile, the oil companies' role in the military's abuses has been acknowledged by the Nigerian government through the Human Rights Violations Investigation Commission. In 2002, it reported that the protection given to oil companies led to 'systematic and generalised violations and abuses'.

Archbishop Welby said in a statement last night: 'During my time at that company [Elf] I worked in a junior finance capacity on a project in Nigeria, travelling to Lagos from Paris.

'To suggest that I was in some way responsible for making strategic decisions, or that I was even aware of any alleged dubious confidential strategy by Elf, is absurd given my youth and lack of seniority.

'In the case of the Bonny LNG project, Elf only had a five per cent stake, so even the company itself had minimal influence in decision making.'

END