Mann was moved from a jail in Harare to Equatorial Guinea in February
Spain and South Africa both "gave the green light" for a failed coup in oil-rich Equatorial Guinea, a British mercenary has told a court in Malabo.
Simon Mann said it felt as though the coup attempt was an official operation.
He also said that Sir Mark Thatcher, son of UK former Prime Minister Margaret Thatcher, was one of the plot's organisers.
But Mann said London-based millionaire Eli Calil was "the boss". He and Sir Mark have both denied plotting a coup.
Sir Mark was fined in 2005 and received a suspended sentence in South Africa for unknowingly helping to finance it.
But former SAS officer Mr Mann, 55, said Sir Mark was part of the "management team... not just an investor".
He was speaking on the second day of his trial, in which Equatorial Guinea prosecutors have called for him to serve 30 years in jail.
If the plot had been successful, veteran Equatorial Guinea opposition leader Severo Moto, then based in Spain, would have become the new president, Mann told the court.
He said Sir Mark had agreed to send a helicopter to transport Mr Moto to the region. Sir Mark has said he believed the helicopter was to be used as an air ambulance.
Mann said the plot was rushed through before the 2004 general elections in Spain, in case the government of Prime Minister Jose Maria Aznar was defeated, Reuters news agency reported.
A Spanish foreign ministry official has denied any involvement.
Mr Mann was arrested four years ago with 64 others in Zimbabwe when they landed in a plane from South Africa.
He served four years in prison there for trying to purchase weapons without a licence before being extradited to Equatorial Guinea earlier this year.
Mann and Sir Mark were neighbours in Cape Town.
The prosecution said they had agreed not to call for the death penalty as part of the deal to extradite him.
The trial is being held at a conference centre in the capital, Malabo, and began amid heavy security.
Journalists were allowed into the courtroom but made to leave mobile phones, cameras and even pens and notepads outside. News reports said that a verdict was expected by Thursday.
Eleven other men, including South African arms dealer Nick Du Toit, who testified that he was recruited by Mr Mann, are already serving sentences in Equatorial Guinea in connection with the coup attempt.
Equatorial Guinea, an oil-rich former Spanish colony, has been ruled by President Teodoro Obiang since he seized power from his uncle in 1979.
His government has been accused of widespread human rights abuses and of ruthlessly suppressing political opposition.
Transparency International has put the tiny nation on its list of top 10 corrupt states.