It has become known as the "Wonga List", an incendiary document said to disclose the identities of the rich and influential public figures who bankrolled the alleged coup attempt in Equatorial Guinea.
The existence of the list has been the subject of speculation within the shadowy international group who allegedly plotted to replace the regime of the West African state and make billions from its oil wealth.
As the plan unravelled and the arrests began, with that of Sir Mark Thatcher the most highly publicised so far, the attempts to get hold of the list by those who had the most to fear from exposure became frantic.
But, The Independent has learnt, the keeper of the secrets - James Kershaw, an accountant and computer expert - is now a witness for the prosecution in South Africa. The list is said to be in the possession of the police and could provide important evidence in trials against the men accused of taking part in the coup plot.
Mr Kershaw, 24, has been named in court by a number of arrested mercenaries as one of the recruiters in the alleged attempt to depose President Teodoro Obiang Nguema. He allegedly made a down payment of $90,000 (£50,000) in the Zimbabwean capital, Harare, and also allegedly gave last-minute instructions, by telephone, to the team.
Mr Kershaw made the decision to co-operate with the authorities after seeking legal advice. A source close to those involved in the incident said: "James is co-operating with the South African authorities and he will give evidence on behalf of the state. He is young, and he got caught up in something he could not really control."
Simon Mann, an Old Etonian, former SAS officer and scion of the Watney brewing dynasty, is on trial in Harare accused of leading the coup attempt.
Apart from Sir Mark, those named as being linked to the mercenaries include Lord Archer, the disgraced peer and former Conservative deputy chairman, and his former financial adviser Ely Calil, a millionaire oil trader of Lebanese extraction.
Documents show that a J H Archer (Lord Archer's initials) paid Mr Mann £74,000 by credit transfer four days before the former soldier was arrested.
Lord Archer's representatives have stressed that he had "no prior knowledge" of the coup and he now "considers the matter closed".
Also drawn into the controversy is the millionaire businessman David Hart, who advised Baroness Thatcher during the miners' strike and remains close to her.Mr Hart was named by Mr Mann in a letter from prison, pleading for help from his friends. Mr Hart has denied any involvement in the alleged coup plot.
It has also emerged that Mr Mann had approached Gianfranco Cicogna, a millionaire telecoms company owner who has among his friends the socialite Taki Theodoracopulos. Mr Cicogna said he refused an invitation to invest in a "project in Equatorial Guinea".
Sir Mark, who is alleged by the South African police to have financed the coup plot, has strenuously denied any culpability. Attention, however, is now focused on his other supposed business ventures in Africa.
Nick du Toit, a South African accused of being part of the mercenary team facing trial in the Equatorial Guinea capital of Malabo, claims that Lady Thatcher's son wanted to purchase helicopters for Sudan. Giving evidencethis week, Mr Du Toit said: "I also sold military helicopters. Thatcher had a mining operation going in Sudan and he wanted two Mi-8 helicopters for Sudan."
Natural resources and their proceeds is one of the sources of conflict between the Sudanese government and African rebel groups. The killings of civilians and ethnic cleansing in Darfur is described by the United Nations as the "worst humanitarian disaster in the world".Reuse content