The former SAS officer Simon Mann has told a court that Sir Mark Thatcher was heavily involved in planning a coup in Equatorial Guinea and not simply the "unwitting" participant in the plot that he claimed to be.
Mr Mann, giving evidence in his own defence at the trial in the country's capital, Malabo, insisted that Baroness Thatcher's son certainly was "not just an investor. He came on board completely and became part of the management team." The London-based businessman Ely Calil, he added, was "the overall boss" of the mission. Mr Calil has always denied any involvement.
The scheme in 2004 to overthrow President Teodoro Obiang Nguema and replace him with Severo Moto Nsa, an opposition leader living in exile in Spain, also had the acquiescence of both Spain and South Africa, said Mr Mann. "It became like a military operation because the Spanish and South African governments were both giving the green light. Their involvement was clandestine and they will never admit it."
A spokesman for Spain's Foreign Ministry denied the claims.
Mr Mann, 55, an Old Etonian heir to a brewery fortune, spoke from the witness box in his prison-issue grey and blue uniform, in a calm and measured voice with his hands clasped behind his back. He had got to know Sir Mark Thatcher, he said, because they were neighbours in the Cape Town suburb of Constantia. He found out that Sir Mark knew Mr Calil and had also been in contact with Mr Moto.
The court heard that Sir Mark paid $300,000 (£150,000) for the purchase of a helicopter to transport Mr Moto from Spain to Equatorial Guinea once Mr Obiang was overthrown. The opposition leader, Mr Mann told the court, would have been transported at first to the Canary Islands off the coast of Africa and then on to Mali. He would have been flown to Malabo when it became clear that the coup had succeeded. The plotters, it is alleged, expected to get highly lucrative contracts once Mr Moto was in power in a country with massive oil reserves.
Mr Mann was arrested in the Zimbabwean capital, Harare, with 70 mercenaries on the way to Equatorial Guinea. An advance party already in Malabo, led by Nick Du Toit, one of Mr Mann's chief lieutenants, was also seized.
Sir Mark was arrested at his home in Cape Town and, in January 2005, fined the equivalent of £266,000 and given a four-year suspended jail sentence. He admitted paying the money to Mr Mann, but maintained that he was under the impression it was going to be spent on an air ambulance service to help the impoverished of Africa. He now lives in San Pedro de Alcantara, in Spain and has refused to comment on the trial in Malabo.
Mr Calil, of Lebanese descent, who made his money out of Nigerian oil deals, had put up $2m for the coup, said Mr Mann. The businessman denies any involvement in the coup and his associates claim Mr Mann has been forced to make the incriminating accusations by the Equatorial Guinea authorities. Mr Mann says Mr Calil misled him into believing that the people of Equatorial Guinea were deeply dissatisfied with Mr Obiang and the country was ripe for a revolution.
He said yesterday: "I am very, very sorry for what I have done, I am also happy that we failed ... I think that the people that were seriously involved in this and have not faced justice, well they should do so now."
In his testimony, Mr Mann presented a scenario of feverish activity and international intrigue as the final touches were applied to the plot. The coup had to be carried out before the Spanish general election on 14 March 2004, said Mr Mann, because there was apprehension among the plotters that the centre-right government of Jose Maria Aznar would fall and the incoming administration might not fulfil the promises of diplomatic and military support which had been made.
"Everything was in a big hurry, because we had this date of 14 March, the Spanish election, which was coming closer and closer," said Mr Mann. "I had been told by Calil that the Aznar government had promised immediate diplomatic recognition if Severo Moto took over." He added that the Spanish government had promised to send a contingent of Guardia Civil and also provide logistical support.
Mr Mann claimed that an intelligence contact had asked him to provide Mr Moto's telephone number so that the South African President, Thabo Mbeki, could call the future president of Equatorial Guinea.
The Foreign Ministry in Madrid rejected the allegations. A spokesman said: " We totally deny what Mr Mann says. We did not give the green light to any of this." South African officials also stated that they had not authorised the enterprise.
Jose Olo Obono, the Equatorial Guinea attorney general, said the next step was for his government to seek the extradition of Sir Mark Thatcher and Mr Calil.
At the start of the trial on Tuesday the prosecution asked for a sentence of 32 years for Mr Mann on charges of crimes against the head of state, crimes against the government and crimes against the peace and independence of the state. The charges carry the death penalty, but Mr Obono explained that waiving capital punishment had been a pre-condition of Mr Mann's extradition from Zimbabwe earlier this year.
Mr Obiang has been in power in Equatorial Guinea since he overthrew his uncle, Francisco Macias Nguema, in 1979. Under his iron rule the country became one of sub-Saharan Africa's biggest oil producers but few have benefited from the petrol boom. Oil revenues are a state secret. Human rights groups say Mr Obiang is one of the worst abusers of rights in Africa.