Elf Aquitaine, until its privatisation in 1994, was much more than a oil company - according to prosecutors at the trial of Elf's top managers.
They claim the state-owned firm worked as an unofficial arm of France's murkiest diplomacy.
The close relationship between Elf and French officials is well-documented, and goes back to the presidency of General Charles de Gaulle.
As the company expanded into Africa in the 1960s and 1970s, Elf paid secret "commissions" to African officials with the blessing of French governments.
Elf had close links with the French state
By the 1980s Elf had operations in Gabon, Congo Brazzaville, Cameroon, Angola and Nigeria - which, investigators say, were kept well oiled by bribes.
But under Loik Le Floch-Prigent - the man appointed to run Elf by socialist President Francois Mitterrand in 1989 - it is claimed that the system went beyond offering sweeteners to secure deals and foster relations with friendly regimes.
Prosecutors say the commissions paid out and received by Elf rocketed from $50m to $130m a year over Mr Le Floch-Prigent's four-year tenure.
This reflects the fact that during that period, Elf ventured beyond France's African sphere of influence and began buying assets in the North Sea, Germany, Spain, Venezuela, Russia, Central Asia and China.
According to investigators, Alfred Sirven - Elf's secretive "director for general affairs" - is said to have handled a fund that was double the size of the one run by the company's man in Africa.
Furthermore, Elf allegedly channelled increasing amounts back to France, where the money found its way to politicians and parties, investigators claim.
As the former socialist foreign minister Roland Dumas recently put it, Elf turned into a "cash-cow".
"Its capital was used to reward African heads of state, but also - one thing leading to another - to bail out certain empty coffers," Mr Dumas said.
In statements made to investigators, Mr Le Floch-Prigent admitted that such illegal payments occurred, but insisted that Elf was just acting as a conduit.
"If the ultimate recipients of the commissions want to have a relationship with such-and-such a French politician or such-and-such a French party, it is their business," he is quoted as saying.
Elf's former boss also says he told Mr Mitterrand that such secret payments could lead to abuse. But - he added - the president insisted that the system set up by General de Gaulle should be retained.
Although 37 former managers are on trial for embezzlement, it is unlikely that politicians who are said to have benefited from the Elf system will ever face justice.
Alfred Sirven once said he knew enough to "topple the Republic 20 times over" - but since his arrest two years ago he has been tight-lipped.
As police caught up with him in the Philippines, Mr Sirven crushed the telephone chip containing details of his latest contacts and ate it - literally swallowing many of his secrets.
The investigation has not been able to shed light on the entire African operation
Judge Renaud van Ruymbeke
Both Mr Sirven and Mr Le Floch-Prigent are serving jail terms, following their 2001 conviction in a separate case connected to Elf saga - the gifts showered on Mr Dumas to try to influence French foreign policy.
Mr Dumas - who was a co-defendant in that case - was cleared on appeal last November.
Judicial investigators have also been frustrated by the lack of government co-operation. The former socialist administration declared that state records on Elf were covered by official secrecy laws.
While prosecutors have examined Swiss bank accounts and say they know how Elf managers used them to acquire properties, jewels, and antiques, they there have drawn a blank on the politically sensitive material.
As Judge Renaud van Ruymbeke, who led the inquiry, put it: "The investigation has not been able to shed light on the entire African operation."